Neutralizing antibodies to HIV-1 and their use

ABSTRACT

Monoclonal neutralizing antibodies are disclosed that specifically bind to the CD4 binding site of HIV-1 gp120. Monoclonal neutralizing antibodies also are disclosed that specifically bind to HIV-1 gp41. The identification of these antibodies, and the use of these antibodies are also disclosed. Methods are also provided for enhancing the binding and neutralizing activity of any antibody using epitope scaffold probes.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. application Ser. No. 14/864,705, filed Sep. 24, 2015, which is a divisional of U.S. application Ser. No. 13/498,125, filed Mar. 23, 2012, which issued as U.S. Pat. No. 9,175,070 on Nov. 3, 2015, which is the U.S. National Stage of International Application No. PCT/US2010/050295, filed Sep. 24, 2010, which was published in English under PCT Article 21(2), which in turn claims the benefit of U.S. Provisional Application No. 61/385,531, filed Sep. 22, 2010, Provisional Application No. 61/402,314, filed Aug. 27, 2010, U.S. Provisional Application No. 61/346,808, filed May 20, 2010, U.S. Provisional Application No. 61/290,135, filed Dec. 24, 2009, U.S. Provisional Application No. 61/252,613, filed Oct. 16, 2009, and U.S. Provisional Application No. 61/246,039, filed Sep. 25, 2009; each of these applications are specifically incorporated by reference herein in their entirety.

FIELD OF THE DISCLOSURE

This relates to monoclonal neutralizing antibodies that bind to the CD4 binding site of HIV-1 gp120 or to HIV-1 gp41, their identification, and their use.

BACKGROUND

An effective HIV-1 vaccine will likely need to induce neutralizing antibodies (NAbs) that block HIV-1 entry into human cells. To be effective, vaccine induced antibodies will have to be active against most circulating strains of HIV-1. Unfortunately, current HIV-1 vaccines are unable to induce potent and broadly reactive NAbs. One major obstacle to the design of better vaccines is the limited understanding of what region of the HIV-1 envelope glycoproteins (gp120 and gp41) are recognized by NAbs. A few neutralizing monoclonal antibodies (mAbs) have been isolated from HIV-1 infected individuals and these mAbs define specific regions (epitopes) on the virus that are vulnerable to NAbs.

One previously characterized HIV-1 neutralizing mAb, called b12, can bind to a site on gp120 that is required for viral attachment to its primary cellular receptor, CD4. Another previously characterized HIV-1 neutralizing mAb, called 2F5, can bind to a site on gp41. mAb b12 was derived from a phage display library, a process which makes it impossible to know if the antibody was naturally present in an infected person, or was the result of a laboratory combination of antibody heavy and light chains. b12 can neutralize about 75% of clade B strains of HIV-1 (those most common in North America), but it neutralizes less than 50% of other strains of HIV-1 found worldwide. Prior attempts to design a vaccine that induces NAbs similar to b12 have been unsuccessful. Therefore, there is a need to develop Nabs for HIV-1.

SUMMARY OF THE DISCLOSURE

Isolated human monoclonal neutralizing antibodies that specifically bind HIV-1 gp120 or gp41 are provided herein. Also disclosed herein are compositions including these antibodies that specifically bind gp120- or gp41-nucleic acids encoding these antibodies, expression vectors comprising the nucleic acids, and isolated host cells that express the nucleic acids. In some embodiments, the heavy chain of the isolated human monoclonal antibody includes amino acids 26-33 (complementarity-determining region 1 (CDR1)), 51-58 (CDR2), and 97-110 (CDR3) of SEQ ID NO: 1, wherein the antibody specifically binds gp120 of HIV-1, and wherein the antibody is neutralizing. In other embodiments, the heavy chain of the isolated human monoclonal antibody includes amino acids 26-35 (CDR1), 50-66 (CDR2), and 106-119 (CDR3) of SEQ ID NO: 27, wherein the antibody specifically binds gp120 of HIV-1, and wherein the antibody is neutralizing. In other embodiments, the heavy chain of the isolated human monoclonal antibody includes CDR1, CDR2, and CDR3 of any one of SEQ ID NOs: 760-1459, wherein the antibody specifically binds gp120 of HIV-1, and wherein the antibody is neutralizing. In still other embodiments, the heavy chain of the antibody includes SEQ ID NO: 5, wherein one or more of amino acids 106, 107, or 109 of SEQ ID NO: 5 are substituted with a tryptophan, and wherein the antibody specifically binds gp41 of HIV-1 and is neutralizing.

The antibodies and compositions disclosed herein can be used for a variety of purposes, such as for detecting an HIV-1 infection or diagnosing AIDS in a subject. These methods can include contacting a sample from the subject diagnosed with HIV-1 or AIDS with a human monoclonal antibody that specifically binds gp120 or gp41, and detecting binding of the antibody to the sample. An increase in binding of the antibody to the sample relative to binding of the antibody to a control sample confirms that the subject has an HIV-1 infection and/or AIDS. In some embodiments, the methods further comprise contacting a second antibody that specifically binds gp120 or gp41 with the sample, and detecting binding of the second antibody. In some non-limiting examples an increase in binding of the antibody to the sample relative to a control sample detects HIV-1 in the subject. In some non-limiting examples, the antibody specifically binds soluble gp120 in the sample. In some embodiments, the methods further comprise contacting a second antibody that specifically recognizes the gp120- or gp41-specific antibody with the sample and detecting binding of the second antibody.

In additional embodiments, a method is disclosed for treating a subject with an HIV infection, such as, but not limited to, a subject with AIDS. The methods include administering a therapeutically effective amount of a human gp120 or gp41 specific monoclonal antibody to the subject.

The foregoing and other features and advantages of this disclosure will become more apparent from the following detailed description of a several embodiments which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A-1E are a set of surface representations and graphs showing the design and antigenic profile of RSC3 and analysis of epitope-specific neutralization. FIG. 1A is a surface structure model of the RSC3. The outer domain contact site for CD4 is highlighted in light grey. Regions highlighted dark are antigenically resurfaced areas, shown both on the inner (left panel) and outer (right panel) faces of the core protein. Glycans are shown in medium grey. FIG. 1B is a set of graphs showing the antigenicity of the RSC3 protein based on enzyme-linked immunosorbent assay (ELISA) using the neutralizing CD4bs mAb b12 and CD4-Ig fusion protein. mAb 2G12 was used to confirm the structural integrity of the protein. FIG. 1C is a set of graphs showing the results of kinetic binding analysis in which mAb b12 was immobilized on the sensor chip for surface plasmon resonance (SPR) kinetic binding analysis with the proteins shown. FIG. 1D is a set of graphs showing the RSC3 blockade of HIV-1 viral strain HXB2 neutralization by the broadly neutralizing CD4bs mAb b12, but not CD4bs mAb F105, which has limited neutralization breadth. The V3 neutralizing mAb 447-52D is shown as a control. FIG. 1E is a set of bar graphs showing the analysis of serum 45 neutralization of a panel of 17 viruses, using RSC3 and ΔRSC3 to block neutralization activity. The percent reduction in the serum ID50 caused by competition with RSC3 or ΔRSC3 is shown on the Y-axis (+/−SEM of three independent experiments). Viral strains and clades are shown on the X-axis. Values less than 20% were not considered significant in this assay.

FIGS. 2A-2C are a set of dot plots and graphs showing isolation of individual CD4bs-directed memory B cells by cell sorting, and binding characterization of isolated mAbs. FIG. 2A is a set of dot plots of flow cytometry data showing the results of twenty-five million peripheral blood mononuclear cells (PBMC) from donor 45 that were incubated with biotin-labeled RSC3 and ΔRSC3 complexed with SA-APC and SA-PE respectively, prior to addition to cells. Memory B cells were selected based on the presented gating strategy. Twenty-nine B cells that reacted with RSC3 and not ΔRSC3 (representing 0.05% of all memory B cells) were sorted into individual wells of a 96 well plate containing lysis buffer. FIG. 2B is a set of graphs of the results of an ELISA antigen binding profile of three isolated mAbs, VRC01, VRC02 and VRC03. Solid lines show mAb binding to RSC3 (left panel) and YU2 gp120 (right panel). Dashed lines indicate binding to ΔRSC3 (left) or to the CD4bs knockout mutant of gp120, D368R (right). FIG. 2C is a set of graphs of the SPR binding analysis of VRC01 reacted with RSC3 and ΔRSC3. VRC01 was captured with an anti-human IgG-Fc antibody that was immobilized on the sensor chip.

FIGS. 3A and 3B are a set of graphs and a table showing the antigenic and biophysical characterization of novel CD4bs-directed mAbs. FIG. 3A is a set of graphs of results of competition ELISA performed with a single concentration of biotin-labeled VRC01 (left) or the co-receptor binding mAb 17b (right). The mAbs indicated near each line were titrated into the ELISA at increasing concentrations to evaluate the effect on VRC01 and 17b binding, respectively. FIG. 3B is a table showing the results of isothermal titration calorimetry (ITC) used to assess the change in enthalpy (ΔH) and entropy (−TΔS) upon binding of mAbs to YU2 gp120. Each measured value is shown +/−SEM.

FIG. 4 is set phylogenetic trees showing the analysis of neutralization by mAbs VRC01 and b12 against a panel of 190 Env pseudoviruses representing all major circulating clades of HIV-1. Dendrograms, made by the neighbor-joining method, show the protein distance of gp160 sequences from 190 HIV-1 primary isolates. The clade B reference strain HXB2 was used to root the tree, and the amino acid distance scale is indicated with a value of 1% distance as shown. The clades of HIV-1 main group, including circulating recombinant forms (CRFs), are indicated. The data under the dendrograms show the percent of viruses neutralized with an IC₅₀<50 μg/ml, and <1 μg/ml, and the geometric mean IC₅₀ value for viruses neutralized with an IC₅₀<50 μg/ml.

FIG. 5A is a schematic drawing showing an algorithm of structure-based design of the resurfaced core proteins. The design intent was to resurface non-CD4bs regions of the core protein, and to maintain the b12 contact surface while abrogating CD4 binding.

FIG. 5B is a protein sequence alignment of the resurfaced proteins RSC2 (SEQ ID NO: 1461), RSC3 (SEQ ID NO: 1462), RC1 (SEQ ID NO: 1464), RC4 (SEQ ID NO: 1465), RC5 (SEQ ID NO: 1465), RC6 (SEQ ID NO: 1466), RC7 (SEQ ID NO: 1468), RC8 (SEQ ID NO: 1469), and the HIV-1 HXB2 core (SEQ ID NO: 1460) or stabilized core (Ds12F123; SEQ ID NO: 1463), which provided the framework for the resurfaced protein designs. Residue positions are marked according to the HXB2 sequence. Highlighted are amino acid substitutions made in the resurfaced proteins in comparison to the original HXB2 core or stabilized core sequences. Gaps are indicated as “-”.

FIG. 6 is a table showing the design and expression of resurfaced core (RC) and resurfaced stabilized core (RSC) glycoproteins, and summary of antigenic reactivity. A panel of 8 resurfaced proteins with different degrees of resurfacing were designed and tested. The surface structural model of each resurfaced protein is shown. Each protein was analyzed for binding to CD4-Ig, b12 and 2G12. 2G12 binding was used as a marker of conformational integrity of the purified protein. ELISA binding activity was categorized as strong (+++), moderate (++), weak (+) or negative (−). RSC3, used subsequently to isolate mAbs, was 31.3% antigenically resurfaced and maintained strong binding to b12.

FIG. 7 is a table showing the results of binding to RSC3 protein by a panel of neutralizing sera. Fifteen clade B sera with moderate to broad neutralizing activity were evaluated by ELISA for binding to RSC3 and ΔRSC3. Neutralization of five viral isolates is shown; the clade of each virus is indicated in parenthesis. Neutralization ID₅₀ values greater than 1000 are highlighted in dark boxes; values between 100-1000 are highlighted in light boxes. ELISA binding was categorized as strong (+++), moderate (++), weak (+) or negative (−). Preferential binding to RSC3, compared to ΔRSC3, is evidence of CD4bs directed antibodies in the sera. Donor 45 was chosen for additional serum analysis, and eventually for isolation of mAbs.

FIG. 8 is a set of graphs showing the comparison of VRC01 and b12 binding kinetics by surface plasmon resonance (SPR). The mAbs were captured with a mouse anti-human IgG Fc antibody that was immobilized onto the chip matrix. The binding kinetics of ligands RSC3, ΔRSC3, stabilized core and full-length YU2 gp120 were analyzed.

FIG. 9 is a set of graphs showing the VRC02 and VRC03 binding kinetics by SPR. The mAbs were captured with a mouse anti-human IgG Fc antibody that was immobilized onto the chip matrix. The binding kinetics of ligands RSC3, ΔRSC3, stabilized core and full-length YU2 gp120 were analyzed.

FIG. 10A is a table showing a gene family analysis of VRC01, VRC02, VRC03 and b12. The VH and VK mutation frequency was calculated from the mutated nucleotides. Mean values from three normal donors consisted of 120 IgD+CD27+ and 97 IgDCD27+ sequences for heavy chain analysis and 167 mutated IgM+ sequences for kappa analysis are shown. A specific D gene could not be determined since the germline genes with the greatest homology (IGHD3/OR15-3, IGHD3-22 or IGHD3-16) each contained a mutation within a matching length of less than 11 nucleotides and the orphan IGHD3/OR15-3 gene on chromosome 15 cannot contribute to Ig chain synthesis; bIGHJ2*01 is an alternative possibility based on the third complementarity determining region 3 (CDR3) sequence analysis; cIGKV3-NL1*01 (NL=Not Located) showed greater homology than IGKV3-11*01 by one nucleotide; dIGKV3-NL5*01 showed greater homology than IGKV3-20*01 by one nucleotide.

FIG. 10B is sequence alignment of the deduced amino acid sequences of the variable regions of VRC01 (heavy chain, SEQ ID NO: 1; light chain, SEQ ID NO: 2), VRC02 (heavy chain, SEQ ID NO: 3; light chain, SEQ ID NO: 4) and VRC03 (heavy chain, SEQ ID NO: 27; light chain, SEQ ID NO: 28). Framework (FR) and CDRs are indicated above the sequence alignment. The top sequence in each group represents the deduced germline sequence with identity to the expressed VH1, D3, JH1, VK3 and JK2 genes. VRC01, VRC02 and VRC03 were derived from the same VH germline gene (IGHV1-02*02, SEQ ID NOs: 41, 42), hence all 3 mAbs are aligned to this sequence. VRC01 and VRC02 are somatic variants of each other (they have the same V-D-J recombination). The arrow marks the position of a 7 amino acids insertion (QLSQDPD, SEQ ID NO: 27) in the VRC03 heavy chain FR3 region. A common motif is underlined in the heavy chain CDR1 (GYXFXD, SEQ ID NO: 27), CDR2 (KPXXGAV, SEQ ID NO: 27) and CDR3 (CDYXXDF, SEQ ID NO: 27). VRC01 and VRC02 have the same VK gene (IGKV3-11*01, SEQ ID NO: 42). While the closest inferred germline sequence match for VRC03 was IGKV3-20*01 (SEQ ID NO: 43), IGKV3-11*01 was also a close match. The dot symbol marks an amino acid deletion in the VK CDR1.

The arrows mark the position of a 2 amino acids insertion (VQ) in VRC01 and VRC02 FR4 (JK gene). Light residues indicate replacement substitutions compared to germline sequence.

FIG. 11A is two graphs showing the results of competition ELISA performed with a single concentration (50 ng/ml) of biotinylated VRC02 or VRC03 binding to YU2 gp120. The unlabeled competing mAbs were titrated into the ELISA at increasing concentrations to evaluate the effect on VRC02 and VRC03 binding respectively.

FIG. 11B are three graphs showing the results of competition ELISA performed with a single concentration (50 ng/ml) of biotinylated VRC01, VRC02 or VRC03 binding to RSC3. The unlabeled competing mAbs were limited to those that showed binding to RSC3.

FIG. 11C is a graph showing the results of analysis of gp120 binding to cell surface expressed CCR5 by flow cytometry. Biotinylated gp120 at 5 μg/ml was used to stain the human CCR5 expressing canine thymus cell line, Cf2Th/syn CCR5. Prior to cell staining, biotinylated gp120 was incubated with CD4-Ig or mAbs VRC01, VRC03 or b12 with serial concentrations ranging from 0.04-25 μg/ml. Binding of gp120 was detected by streptavidin-APC and FACS analysis. Note that CD4-Ig and VRC01 enhanced gp120 binding to CCR5, while mAbs b12 and VRC03 did not.

FIGS. 12A and 12B are a set of graphs showing analysis of the effect of VRC01 on the functional viral spike. FIG. 12A is a set of graphs showing the neutralization of JRFL that was performed with the mAbs shown in the legend. Antibody 447-52D is directed to the V3 region of gp120, and mAbs 17b and vc813DB are directed to the co-receptor binding region of gp120. Graphs show the effect on neutralization as sCD4 (left panel) or VRC01 (right panel) were added to the assay. The adjusted neutralization was calculated using the baseline of viral entry at each concentration of sCD4 or VRC01. In contrast to sCD4, VRC01 did not enhance the neutralization by mAbs 447-52D, 17b and vc813DB. FIG. 12B is a set of graphs showing JRFL entry into the CCR5+/CD4− cell line, Cf2Th/syn CCR5. CD4-Ig and sCD4 (left panel) promote entry of JRFL into CD4 negative cells. VRC01 (right panel) did not promote viral entry. Each infection was performed in triplicate, and the mean and standard error are shown.

FIGS. 13A and 13B are a table and a graph showing correlation analysis of neutralization by serum 45 IgG and mAb VRC01. FIG. 13A is a contingency table showing neutralization by serum 45 IgG and mAb VRC01. Fisher's exact test demonstrated a strong association between the number of viruses neutralized by serum 45 IgG and mAb VRC01. Serum 45 IgG sensitive was defined as an IC50<1000 μg/ml. VRC01 sensitivity was defined as an IC50<50 μg/ml. FIG. 13B is a graph of a deming regression analysis of log transformed IC50 values of viruses neutralized by both VRC01 and serum 45 IgG. This showed a strong association between the potency of serum 45 IgG and mAb VRC01. The slope of the regression line is 0.68 (95% CI 0.07). Thus, while VRC01 accounts for a substantial portion of total serum 45 IgG neutralization, the slope of less than 1.0 suggests that VRC01 does not account for all serum 45 IgG neutralization activity.

FIG. 14 is Table 51 showing the ELISA binding profiles of VRC01, VRC02, and VRC03 compared to a panel of known mAbs.

FIG. 15 is Table S2a showing a summary of the breath and potency of antibody neutralization against 190 HIV-1 Env-pseudoviruses.

FIG. 16 is Table S2b showing antibody neutralization data against 22 HIV-1 clade A HIV-1 Env-pseudoviruses.

FIGS. 17A and 17B are Table S2c showing antibody neutralization data against 49 HIV-1 clade B HIV-1 Env-pseudoviruses.

FIGS. 18A and 18B are Table S2d showing antibody neutralization data against 38 HIV-1 clade C HIV-1 Env-pseudoviruses.

FIG. 19 is Table S2e showing antibody neutralization data against 8 HIV-1 clade D HIV-1 Env-pseudoviruses.

FIG. 20 is Table S2f showing antibody neutralization data against 18 HIV-1 CRF01_AE Env-pseudoviruses.

FIG. 21 is Table S2g showing antibody neutralization data against 16 HIV-1 CRF02_AG Env-pseudoviruses.

FIG. 22 is Table S2h showing antibody neutralization data against 10 HIV-1 clade G Env-pseudoviruses.

FIG. 23 is Table S2i showing antibody neutralization data against 11 HIV-1 CRF07_BC Env-pseudoviruses.

FIG. 24 is Table S2j showing antibody neutralization data against 18 Env-pseudoviruses.

FIG. 25 is Table S3 showing IC50 titers (μg/ml) of antibody neutralization against selected HIV-1 clade B and C viruses using Env-pseudoviruses to infect TZM-bl or activated PBMC, and using PBMC derived uncloned primary isolates to infect TZM-bl or activated PBMC.

FIG. 26 is an electronic image of a depiction of the structure of antibody VRC01 in complex with HIV-1 gp120. Atomic-level details for broad and potent recognition of HIV-1 by a natural human antibody are depicted with polypeptide chains in ribbon representations. Both light and heavy chains of VRC01 interact with gp120: the primary interaction surface is provided by the CDR H2, with the CDR L1 and L3 and the CDR H1 and H3 providing additional contacts.

FIGS. 27A-27D are a set of electronic images depicting the structural mimicry of CD4 interaction by antibody VRC01. VRC01 shows how a double-headed antibody can mimic the interactions with HIV-1 gp120 of a single-headed member of the immunoglobulin superfamily such as CD4. FIG. 27A is a comparison of HIV-1 gp120 binding to CD4 (N-terminal domain) and VRC01 (heavy chain-variable domain). Polypeptide chains are depicted in ribbon representation for the VRC01 complex (right) and the CD4 complex with the lowest gp120 RMSD (left). Immunoglobulin domains are composed of two β-sheets, and the top sheet of both ligands is labeled with the standard immunoglobulin-strand topology (strands G, F, C, C′, C″). Close-ups are shown of critical interactions between the CD4-binding loop and the C″ strand as well as between Asp368gp120 and either Arg59CD4 or Arg71VRC01. Atoms from which hydrogen bonds extend are depicted in stick representation. In the left panel of C, the β15-strand of gp120 is depicted to aid comparison with FIG. 27B, though because of the poor hydrogen-bond geometry, it is only a loop. FIG. 27D shows the comparison of VRC01- and CD4-binding orientations. When the heavy chain of VRC01 is superimposed onto CD4 in the CD4-gp120 complex, the position assumed by the light chain evinces numerous clashes with gp120 (left). The VRC01-binding orientation (right) avoids clashes by adopting an orientation rotated by 43° and translated by 6-Å.

FIGS. 28A-28C are a dendrogram, a bar graph, and a set of graphs showing structural basis of antibody VRC01 neutralization breadth and potency. VRC01 displays remarkable neutralization breadth and potency, a consequence in part of its ability to bind well to different conformations of HIV-1 gp120. FIG. 28A shows neutralization dendrograms. The genetic diversity of current circulating HIV-1 strains is displayed as a dendrogram, with locations of prominent clades (e.g. A, B and C) and recombinants (e.g., CDR02_AG) labeled. VRC01 neutralizes 72% of the tested HIV-1 isolates with an IC80 of less than 1 ug/ml; by contrast, CD4 neutralizes 30% of the tested HIV-1 isolates with an IC80 of less than 1 ug/ml. FIG. 28B shows a comparison of binding affinities. Binding affinities (KDs) for VRC01 and various other gp120-reactive ligands as determined by surface-plasmon resonance are shown on a bar graph. White bars represent affinities for gp120 restrained from assuming the CD4-bound state and black bars represent affinities for gp120 fixed in the CD4-bound state. Binding too weak to be measured accurately is shown as with an asterisk and bar at 10⁻⁵ M KD. FIG. 28C shows the neutralization of viruses with altered sampling of the CD4-bound state. Mutant S375Wgp120 favors the CD4-bound state, whereas mutants H66Agp120 and W69Lgp120 disfavor this state. Neutralization by VRC01 (left) is similar for wild-type (WT) and all three mutant viruses, whereas neutralization by CD4 (right) correlates with the degree to which gp120 in the mutant viruses favors the CD4-bound state.

FIGS. 29A-29D are electronic images depicting the natural resistance to antibody VRC01. VRC01 precisely targets the CD4-defined site of vulnerability on HIV-1 gp120. Its binding surface, however, extends outside of the target site, and this allows for natural resistance to VRC01 neutralization. FIG. 29A shows the target site of vulnerability. The CD4-defined site of vulnerability is the initial contact surface of the outer domain of gp120 for CD4 and comprises only two-thirds of the contact surface of gp120 for CD4. The view shown here is rotated 90° about the horizontal from the view in FIGS. 26 and 27. FIG. 29B shows VRC01 recognition. The variable domains of VRC01 are shown in ribbon representation. FIG. 29C shows antigenic variation. FIG. 29D, shows a molecular surface of VRC01 and select interactive loops of gp120. Variation at the tip of the V5 loop is accommodated by a gap between heavy and light chains of VRC01.

FIGS. 30A-30D are a set of electronic images, bar graphs and graphs depicting the unusual VRC01 features. The structure of VRC01 displays a number of unusual features, which if essential for recognition might inhibit the elicitation of VRC01-like antibodies. In FIG. 30A-30D, unusual features of VRC01 are shown structurally (far left panel), in terms of frequency as a histogram with other antibodies (second panel from left), and in the context of affinity and neutralization measurements after mutational alteration (right two panels). Affinity measurements were made by ELISA to the gp120 construct used in crystallization (93TH057), and neutralization measurements were made with a clade A HIV-1 strain Q842.d12. FIG. 30A shows N-linked glycosylation. The conserved tri-mannose core is shown with observed electron density, along with frequency and effect of removal on affinity. FIG. 30B shows an extra disulfide. Variable heavy domains naturally have two Cys, linked by a disulfide; VRC01 has an extra disulfide linking CDR H1 and H3 regions. This occurs rarely in antibodies, but its removal by mutation to Ser/Ala has little effect on affinity. FIG. 30C shows CDR L1 deletion. A two amino acid deletion in the CDR L1, prevents potential clashes with loop D of gp120. Such deletions are rarely observed; reversion to the longer loop may have a 10-100-fold effect on gp120 affinity. FIG. 30D shows the somatically altered contact surface. The far left panel shows the VRC01 light chain and heavy chain. Residues altered by affinity maturation are depicted with “balls” and contacts with HIV-1 gp120 are colored red. About half the contacts are altered during the maturation process. Analysis of human antibody-protein complexes in the protein-data bank shows this degree of contact surface alteration is rare; reversion of each of the contact site to genome has little effect though in aggregate the effect on affinity is larger.

FIGS. 31A-31B are a set of graphs showing somatic maturation and VRC01 affinity. Hypermutation of the variable domain during B cell maturation allows for the evolution of high affinity antibodies. With VRC01 this enhancement to affinity occurs principally through the alteration of noncontact residues, which appear to reform the genomic contact surface from affinity too low to measure to a tight (nM) interaction. FIG. 31A shows the effect of genomic reversions. The VH- and VK-derived regions of VRC01 were reverted to the sequences of their closest genomic precursors, expressed as immunoglobulins and tested for binding as VH- and VK-revertants (gHgL), as a VH-only revertant (gH), or as a VK-only revertant (gL) to the gp120 construct used in crystallization (93TH057) or to a stabilized HXBc2 core. These constructs were also tested for neutralization of a clade A HIV-1 strain Q842.d12. FIG. 31B shows maturation of VRC01 and correlation with binding and neutralization. Affinity and neutralization measurements for the 19 VRC01 mutants created during the structure-function analysis of VRC were analyzed in the context of their degree of affinity maturation. Significant correlations were observed, with extrapolation to VH- and VK-genomic revertants suggesting greatly reduced affinity for gp120.

FIG. 32 is a gp120 sequence alignment and residue-by-residue contacts with CD4 and VRC01. Both wild type clade B HXBc2 (SEQ ID NO: 44) and clade A/E 93TH057 core gp120 sequences (SEQ ID NO: 45) are displayed with HXBc2 numbering convention. The 93TH057 construct has shorter V1/V2 stem and has a new V3 stem. gp120 contacts are defined with the program PISA for the CD4 and VRC01 complexes, with open circles (◯) denoting gp120 main-chain-only contacts, open circles with rays (¤) denoting gp120 side-chain-only contacts, and filled circles (●) denoting both main-chain and side-chain contacts. The major structure elements of gp120 that involved in ligand binding were underlined. Potential glycosylation sites on gp120 with signature sequence NXT/S are highlighted in cyan, however, not all sites are observed in the crystal structure. VRC01 has remarkably less interactions with the conformationally variable V1/V2 and β20/β21 regions and more interactions at the loop D and V5 areas.

FIG. 33 is a set of electronic images showing electrostatic surfaces and maps of residues types of gp120. Electrostatic surfaces for the VRC01 and CD-bound gp120s are shown in the left panels with heavy chain variable domain (VH) of VRC01 (upper row) and domain 1 (D1) of CD4 (lower row). Both of VRC01 and CD4 bind to overall negatively charged surfaces on gp120. The flip sides of the complexes showing the electrostatic surfaces of VH and D1 are presented in the middle panels with gp120 in the foreground. The gp120 interfaces on VH of VRC01 and D1 of CD4 are mostly positively charged to complement the negatively charged gp120 surfaces. Certain residues, such as Arg71 in VRC01 and Arg59 in CD4, are conserved, the unique VRC01 Arg61 that penetrating the cavity formed by V5 and β24 is also shown. The electrostatic potential was calculated with APBS and visualized with Pymol.

FIG. 34 is a set of graphs showing the binding of VRC01 to gp120 stabilized in CD4-bound and non-CD4-bound conformations. Both gp120 in non-CD4-bound conformation (YU2 Δβ4) and gp120 stabilized in CD4-bound conformation (HXBc2 core Ds12F123) were immobilized on a CM-5 chip. Fabs of CD4-binding site antibodies VRC01, b12 and F105 and CD4-induced antibody 17b, two domain CD4 and CD4-IgαTP at various concentrations were injected over the chip channels.

FIGS. 35A and 35B are a set of electronic images and a bar graph showing a comparison of coverage of the site of vulnerability by different CD4-binding site antibodies. The site of vulnerability is the contact site for receptor CD4 on the outer domain of gp120. CD4-binding-site-directed antibodies target this general area, however, most of them do not neutralize potently. FIG. 35A shows that when the site of vulnerability is superimposed over the antibody epitopes on gp120 surfaces, the degrees of overlapping differ. VRC01 hits the “bull's-eye” while b12, b13 and F105 miss portions of the target with epitope straying away to other conformationally variable areas on gp120. FIG. 35B shows that when coverage of the site of vulnerability by epitopes of CD4-binding-site-directed antibodies were compared, VRC01 achieves almost full coverage (98%) while others, such as b13, F105 and b12, manage to get 50% to 83% overlapping coverage with CD4.

FIGS. 36A-36D are a set of electronic images and a sequence alignment showing the mechanism of natural resistance to VRC01. FIG. 36A shows a sequence threading of the 17 HIV-1 isolates that resist neutralization by VRC01. Spots that are closer than 2.5 Å to VRC01 are dark. These spots are clustered at the loop D and V5 region on HIV-1gp120. FIG. 36B shows a close-up of threaded, resistant isolates along with the molecular surface of VRC01. FIG. 36C shows VRC01 heavy chain Arg61 penetrating the gp120 cavity formed by V5 and β24. Some resistant isolates have bulky residues pointing into the cavity which interfere with Arg61VRC01 without affecting CD4 binding. FIG. 36D shows a sequence alignment of VRC01-resistant isolates at the V5 region (SEQ ID NO: 46). Black boxes highlight bulky residues that may interfere with binding of VRC01 and are different from the 93TH057 sequence. Different N-linked glycosylation patterns are also marked.

FIG. 37 is an electronic image showing the conformational variation of gp120 loopV5. Side-by-side comparison of conformation variation at the HIV-1 gp120 variable loop 5 region indicates that the four gp120 components (left panel, chains G, A, D and I) of the VRC01:gp120 complexes in the crystallographic asymmetric unit vary only at the tip of V5 loop and conformation of the V5 base is less flexible due to increased contacts by VRC01. In contrast, variation of V5 conformations in other gp120 complexes (right panel) with CD4 and CD4-binding site antibodies, F105, b12 and b13, spans over the whole range of V5 loop.

FIGS. 38A-38D are electronic images showing that VRC01 recognition of V5 and β24 of gp120 is different from that of CD4. FIGS. 38A and 38B illustrate that the V5 loop is wedged in the gap formed by the heavy and light chains of VRC01, meanwhile, Arg61 in the CDRH2 penetrates into the cavity formed by gp120 V5 and β24, locking V5 into a less flexible conformation. In contrast, CD4 only interacts with the “front side” of V5. FIGS. 38C and 38D illustrates that VRC01 engages extensive interactions with V5 and β24 with 10 hydrogen bonds and a salt bridge from both CDR H2 and CDR L3. While heavy chain Asn68, Gln64 and light chain Glu96 grab the front side of V5, heavy chain Arg61 goes behind the V5 and provides 4 hydrogen bonds to residues on β24. CD4, however, only has 3 hydrogen bonds to 2 V5 residues. It is worth to note that VRC01 only interacts with residues at the base of V5 loop and avoids the loop tip which has higher degree of sequence variation. The VRC01 CDRs are shown. Selected gp120 residues are labeled in italic.

FIG. 39 is a set of electronic images showing the key interface regions of the gp120:VRC01 complex. gp120-interacting CDRs of VRC01 are projected over the gp120 surface (left panel). Both heavy and light chains are involved in binding of gp120, mainly to the conformationally invariant outer domain. The CDR H2 spans over the CD4-binding loop and the V5/β24, with Arg61 penetrating the V5/β24 cavity (right panel). Arg71 in the framework 3 forms salt bridges with a conserved Asp368 in the CD4-binding loop of gp120. The light chain of CDRL1 and CDRL3 provide interactions to V5, loop D as well as the Loop D attached N-acetyl-glucosamine of a N-linked glycan.

FIG. 40 is an alignment of the VRC01 sequence, gp120 contacting-sites and extent of affinity maturation. The sequence of VRC01 (SEQ ID NO: 1 and SEQ ID NO: 2) is shown along with nearest VH- and VK/λ-genomic precursors for heavy (SEQ ID NO: 41) and light chain (SEQ ID 42), respectively. Affinity maturation changes are indicated in green, with residues involved in interaction with HIV-1 gp120 highlighted by “●”, if involved in both main- and side-chain interactions, by “◯” if main chain-only, and by “¤” if side chain-only. “

” marks a site of N-linked glycosylation, “▴” for Cysteine residues involved in a noncanonical disulfide, and “Δ” if the residue has been deleted during affinity maturation.

FIG. 41 is a bar graph showing the contact, V-gene mutated, and mutated contact residues for the set of 26 antibodies and VRC01. Any antibody residue in contact with the antigen in the complex is included towards the total number of contact residues. The number of mutations from germline for the Vh and Vl/Vk, as well as the number of mutated contact residues are shown. The number of mutations excludes insertions and deletions. Germline alignment was performed using the amino acid sequences for the antibody heavy and light chains. For comparison, also shown is the number of mutated residues (total and only contact residues) when germline alignment is performed for the **VRC01 nucleotide sequence.

FIG. 42 is an electronic image showing of the contributions of VRC01 VH-D-J and VK-J fragments to the binding of HIV-1 gp120. The variable domains of VRC01 are shown in cartoon diagram and the gp120 binding areas are masked with a surface.

FIG. 43 is the alignment of VRC01 Vh (SEQ ID NO: 1) to the ten closest germline genes. Results were obtained from IgBLAST using the VRC01 Vh nucleotide sequence. Residue identities are shown as dots. The nucleotide identity fraction for each of the ten germline genes, as reported by IgBLAST, is also shown.

FIG. 44 is the alignment of VRC01 Vk (SEQ ID NO: 2) to the ten closest germline genes. Results were obtained from IgBLAST using the VRC01 Vk nucleotide sequence up to amino acid residue Q90; since IGKV3-NL1*01 is ‘not localized’, IGKV3-11*01 was selected as a top match for the Vk germline. When comparing to IGKV3-11*01 using nucleotide sequences, the two-residue deletion in VRC01 Vk aligns to two S residues and involves a neighboring S→Y mutation. Residue identities are shown as dots. The nucleotide identity fraction for each of the ten germline genes, as reported by IgBLAST, is also shown.

FIGS. 45A-45C is a set of graphs showing the results of a sequence comparison of VRC01, VRC02 and VRC03 to a collection of gp140-binding antibodies. FIG. 45A is a VH and Vk repertoire analysis for a collection of gp140-binding antibodies and VRC01, 02 and 03. The pie charts display the distribution of V gene usage among the collection of unique antibodies. VRC01, 02, 03 genes are indicated with red arrows. FIG. 45B shows a CDR amino acid length of the collection of antibodies compared to VRC01, 02 and 03 indicated with a red arrow. CDR3 lengths were determined according to NCBI IgBlast nomenclature with the CDR3 region starting after the CTR and CVR amino acids for VRC01, 02 and 03, respectively. FIG. 45C shows the number of nucleotide mutations in the V genes of the antibody collection compared to VRC01, 02 and 03.

FIGS. 46A-46F are a set of graphs showing the correlations between the number of affinity matured residues in VH and Vk and SPR determined dissociation constants, ELISA (EC50) binding, and neutralization (IC50) data for a set of VRC01 variants. VRC01 variants were made to revert interface residues to their corresponding VH- and Vkgermline-encoded residues in a series of single-, 4-, 7- or 12-residue mutations.

FIG. 47 is Table S1.

FIG. 48 is Table S2.

FIG. 49 is Table S3.

FIG. 50 is Table S4.

FIG. 51 is Table S5.

FIG. 52 is Table S6.

FIG. 53 is Table S7.

FIG. 54 is Table S8.

FIG. 55 is Table S9.

FIG. 56 is Table S10a.

FIGS. 57A and 57B are Table S10b.

FIG. 58 is Table S11.

FIGS. 59A and 59B are Table S12.

FIG. 60 is Table S13.

FIG. 61 is Table S14.

FIGS. 62A-62C is a set of electronic images a sequence alignment and a bar graph showing F5 CDR H3 loop mutagenesis (SEQ ID NOs: 47-58). FIG. 62A illustrates the structure of 2F5 Fab in complex with a gp41 peptide. The 2F5 CDR H3 contacts gp41 only at its base, while the tip extends away from the peptide. FIG. 62B is a close-up view of the 2F5 CDR H3 loop. FIG. 62C shows mutations introduced into the tip of the 2F5 CDR H3 (100A to 100F) along with a plot of the Wimley-White predicted free energies of transfer to a lipid bilayer interface or to octanol for each of the mutations.

FIG. 63 is Table 1.

FIG. 64 is a set of graphs showing the neutralization of HxB2 by CDR H3 mutants of antibody 2F5. Top, neutralization profiles of 2F5 variants with single mutations to serine. Single serine substitutions resulted in a 15- to 500-fold reduction in neutralization potency. Middle, neutralization profiles of double mutations to serine. Double serine substitutions completely abrogated 2F5-mediated neutralization. Bottom, neutralization profiles of 2F5 variants with mutations to tryptophan. Tryptophan substitutions were either commensurate with or more potent than wild-type 2F5. Neutralization curves for wild-type 2F5 IgG are colored black and are shown in all three panels. 1D4, mouse anti rhodopsin antibody used as a negative control.

FIGS. 65A-65C are a set of graphs showing the relationship between 2F5-mediated HIV-1 neutralization and the hydrophobicity of its CDR H3 loop. FIG. 65A shows 2F5 variant neutralization IC50s plotted against the calculated ΔG_(wif) of the 2F5 CDR H3 loop for each virus strain tested. Linear regressions were fit to each individual group, and no significant differences were observed in the slopes of each of the curves. The resulting P values of the correlations were statistically significant (P<0.02) for all strains tested, with the exception of RHPA-4259. FIG. 65B shows 2F5 variant neutralization IC50s plotted against affinity to gp41 MPER peptide, with linear fits applied to each group. No statistically significant associations were observed in this case, and the regressions appeared largely driven by the KD of 2F5 variant I100FS to gp41, likely because of minor contacts made by this residue with gp41. FIG. 65C shows plots of relative free energies of neutralization (ΔΔG^(N)) versus calculated ΔG_(wif) values, along with individual solid lines) and shared (dashed black line and displayed statistics) linear fits for all strains tested. HIV strains are represented as symbols and lines. The dashed vertical lines define the ΔG_(wif) value of the wild-type 2F5 CDR H3 tip or the KD of wild-type 2F5 to gp41 peptide.

FIG. 66 is Table 2.

FIGS. 67A-67C are a depiction of the threshold for effects of increased 2F5 CDR H3 loop hydrophobicity. To account for the observed leveling off of the effects of increased 2F5 CDR H3 loop hydrophobicity, quadratic fits were applied to the data shown in FIG. 66. FIG. 67A, 2F5 variant neutralization IC50s plotted against the calculated ΔG_(wif) of the 2F5 CDR H3 loop for each virus strain tested. Individual curves were fit to each group using a quadratic regression model, which revealed no significant differences in their slopes or quadratic terms. FIG. 67B, plot of relative free energies of neutralization (ΔΔG^(N)) versus calculated ΔG_(wif). As in panel A, individual curves were fit to each group using a quadratic regression model, which revealed no significant differences in their slopes or quadratic terms. FIG. 67C, the quadratic models were refit to the data using common estimates of the slopes and quadratic terms and plotted as a shared quadratic regression for all strains tested (dashed black line). A minimum of the ΔΔG^(N) was observed to occur at a ΔG_(wif) of −4.08 kcal/mol (arrow), representing the maximal effect on neutralization beyond which increased hydrophobicity of the CDR H3 loop had detrimental effects on 2F5-mediated neutralization. HIV strains are represented as symbols and lines. The dashed vertical lines (gray) define the ΔG_(wif) value of the wild-type 2F5 CDR H3 tip.

FIG. 68 is schematic representation of the two-component mechanism of 2F5-mediated neutralization of HIV-1. The free energy of 2F5-mediated neutralization of HIV-1, ΔG^(N) (diagonal), can be expressed as the sum of the free energy of its structure-specific recognition of its gp41 MPER epitope (vertical component) combined with the free energy of nonspecific interactions mediated by the hydrophobic tip of its CDR H3 loop (horizontal component). Structural representations of each component are shown.

FIG. 69 is Table s1.

FIG. 70 is Table s2.

FIG. 71 is Table s3.

FIG. 72 is a set of graphs showing the results of surface plasmon resonance binding profiles of 2F5 variants to gp41 peptide. Shown are representative biacore binding profiles of gp41-MPER-C9 peptide to wild-type and mutant 2F5 IgG's (black), overlaid with fits of the data. In all cases, IgGs were directly coupled to CMS chips, and the peptide was used as analyte. Plotted analyte concentrations are 2-fold serial dilutions ranging from 31 nM to 0.49 nM, except for 2F5 variant L100AS-F100BS, which ranged from 15 nM to 0.49 nM, and variants L100ASV100DS and F100BS-I100FS, which ranged from 125 nM to 0.49 nM. In all cases, nanomolar binding affinity to gp41 peptide was maintained.

FIGS. 73A-73D is a set of graphs of the relationship between HIV-1 neutralization and ΔG_(oct), hydrophobicity of 2F5 CDR H3 P<0.0001 variants. FIG. 73A, 2F5-variant neutralization IC50s plotted against calculated ΔG_(oct), of the 2F5 CDR H3 loop, for each virus strain tested. Linear regressions were fit to each individual group, and no significant differences were observed in their slopes. The resulting P-values of the correlations were all statistically significant (P<0.05), with the exception of RHPA-4259. FIG. 73B shows that quadratic regressions fit to the same data as in FIG. 73A, reveal no significant differences in the slopes or quadratic terms. Plots of relative free energies of neutralization (ΔΔG^(N)) versus calculated ΔG_(oct), were fit with linear (FIG. 73C) and quadratic regression models (FIG. 73D), as shown. Shared regressions across all strains in FIG. 73C and FIG. 73D are represented as dashed black lines. A dashed vertical line defines the ΔG_(oct) properties of the wild-type 2F5 CDR H3 tip.

FIG. 74A is a schematic diagram and the sequence of VRC01 ImmunoAdhesin HL (SEQ ID NO: 66).

FIG. 74B is a schematic diagram and the sequence of VRC01 ImmunoAdhesin LH (SEQ ID NO: 66).

FIGS. 75A-75E is a series of schematic diagrams for VRC8551, VRC8552, VRC9709, VRC9710, VRC9711, VRC9712, VRC9713, VRC9714, VRC9715, VRC9716, VRC9717, VRC9712, VRC9713 and VRC9174.

FIG. 76 is a table and an electronic image of a protein gel showing the expression of chimeras of VRC01 and VRC03.

FIG. 77 is a set of graphs showing exemplary neutralization data for clade A HIV viruses obtained from VRC01 and VRC03 chimeric antibodies.

FIG. 78 is a set of graphs showing exemplary neutralization data for clade B HIV viruses obtained from VRC01 and VRC03 chimeric antibodies.

FIG. 79 is a set of graphs showing exemplary neutralization data for clade C HIV viruses obtained from VRC01 and VRC03 chimeric antibodies.

FIG. 80 is a sequence alignment of the amino acid sequence of the heavy chain of antibody 57203 (SEQ ID NO: 1322) identified by 454 sequencing, the germline sequence IGHV1-02*02 (SEQ ID NO: 41), VRC01 (SEQ ID NO: 1), VRC02 (SEQ ID NO: 3) and VRC03 (SEQ ID NO: 27).

FIGS. 81A-81H are a set of graphs of exemplary neutralization data of the 57203 heavy chain VRC01 light chain chimera demonstrating that the 57203 is VRC01 like, in that it complements the VRC01 light chain.

FIG. 82 is a graph showing the distribution of the VRC01 and VRC03 sequences set for as SEQ ID NOs: 760-1459.

FIGS. 83-90, 91A, 91B and 93-97 are supporting data showing the conserved gp120 epitope common to the binding site of VRC01 and VRC03-like antibodies.

FIGS. 92A-92G show the production of VCR01 multimers.

FIGS. 98-117 are supporting data showing bioinformatics analysis.

SEQUENCE LISTING

The nucleic and amino acid sequences listed in the accompanying sequence listing are shown using standard letter abbreviations for nucleotide bases, and three letter code for amino acids, as defined in 37 C.F.R. 1.822. Only one strand of each nucleic acid sequence is shown, but the complementary strand is understood as included by any reference to the displayed strand. The Sequence Listing is submitted as an ASCII text file in the form of the file named “Sequence_Listing.txt” (˜1.3 MB), which was created on Jul. 24, 2017, which is incorporated by reference herein. In the accompanying sequence listing:

SEQ ID NO: 1 is the amino acid sequence of the heavy chain of gp120-specific antibody VRC01.

SEQ ID NO: 2 is the amino acid sequence of the light chain of gp120-specific antibody VRC01.

SEQ ID NO: 3 is the amino acid sequence of the heavy chain of gp120-specific antibody VRC02.

SEQ ID NO: 4 is the amino acid sequence of the light chain of gp120-specific antibody VRC02.

SEQ ID NO: 5 is the amino acid sequence of the heavy chain of gp41-specific antibody 2F5.

SEQ ID NO: 6 is the amino acid sequence of the heavy chain of gp41-specific antibody 2F5 L_(100A)W.

SEQ ID NO: 7 is the amino acid sequence of the heavy chain of gp41-specific antibody 2F5 F_(100B)W.

SEQ ID NO: 8 is the amino acid sequence of the heavy chain of gp41-specific antibody 2F5 V_(100D)W.

SEQ ID NO: 9 is the amino acid sequence of the heavy chain of gp41-specific antibody 2F5 L_(100A)W-V_(100D)W.

SEQ ID NO: 10 is the amino acid sequence of the light chain of gp41-specific antibody 2F5.

SEQ ID NO: 11 is the gp41 MPER Epitope Scaffold Immunological Probe ES1 (1LGYA) Clade B.

SEQ ID NO: 12 is the gp41 MPER Epitope Scaffold Immunological Probe ES1 (1LGYA) Clade B point mutant.

SEQ ID NO: 13 is the gp41 MPER Epitope Scaffold Immunological Probe ES1 (1LGYA) Clade C.

SEQ ID NO: 14 is the gp41 MPER Epitope Scaffold Immunological Probe ES2 (1KU2A-s) Clade B.

SEQ ID NO: 15 is the gp41 MPER Epitope Scaffold Immunological Probe ES2 (1KU2A-s) Clade B point mutant.

SEQ ID NO: 16 is the gp41 MPER Epitope Scaffold Immunological Probe ES2 (1KU2A-s) Clade C.

SEQ ID NO: 17 is the gp41 MPER Epitope Scaffold Immunological Probe ES3 (2MATA) Clade B.

SEQ ID NO: 18 is the gp41 MPER Epitope Scaffold Immunological Probe ES3 (2MATA) Clade B point mutant.

SEQ ID NO: 19 is the gp41 MPER Epitope Scaffold Immunological Probe ES3 (2MATA) Clade C.

SEQ ID NO: 20 is the gp41 MPER Epitope Scaffold Immunological Probe ES4 (1IWLA) Clade B.

SEQ ID NO: 21 is the gp41 MPER Epitope Scaffold Immunological Probe ES4 (1IWLA) Clade B point mutant.

SEQ ID NO: 22 is the gp41 MPER Epitope Scaffold Immunological Probe ES4 (1IWLA) Clade C.

SEQ ID NO: 23 is the gp41 MPER Epitope Scaffold Immunological Probe ES5 (1D3BB) Clade B.

SEQ ID NO: 24 is the 41 MPER Epitope Scaffold Immunological Probe ES5 (1D3BB) Clade B point mutant.

SEQ ID NO: 25 is the 41 MPER Epitope Scaffold Immunological Probe ES5 (1D3BB) Clade C.

SEQ ID NO: 26 is the Avitag amino acid sequence.

SEQ ID NO: 27 is the amino acid sequence of the heavy chain of gp120-specific antibody VRC03.

SEQ ID NO: 28 is the amino acid sequence of the light chain of gp120-specific antibody VRC03.

SEQ ID NO: 29 is the nucleic acid sequence of the heavy chain of gp120-specific antibody VRC01.

SEQ ID NO: 30 is the nucleic acid sequence of the light chain of gp120-specific antibody VRC01.

SEQ ID NO: 31 is the nucleic acid sequence of the heavy chain of gp120-specific antibody VRC02.

SEQ ID NO: 32 is the nucleic acid sequence of the light chain of gp120-specific antibody VRC02.

SEQ ID NO: 33 is the nucleic acid sequence of the heavy chain of gp120-specific antibody VRC03.

SEQ ID NO: 34 is the nucleic acid sequence of the light chain of gp120-specific antibody VRC03.

SEQ ID NO: 35 is the nucleic acid sequence of VRC01 ImmunoAdhesin HL.

SEQ ID NO: 36 is the amino acid sequence of an exemplary mouse interleukin-2 (IL-2) leader sequence.

SEQ ID NO: 37 is the amino acid sequence of an exemplary gp120 V1/V2 loop.

SEQ ID NO: 38 is the amino acid sequence of an exemplary gp120 V3 loop.

SEQ ID NO: 39 is the amino acid sequence of an exemplary peptide linker.

SEQ ID NO: 40 is the amino acid sequence of an en exemplary peptide corresponding to residues 657 to 669 of linked to a C-terminal C9 tag.

SEQ ID NO: 41 is the amino acid sequence of the heavy chain of IGHV1-02*02.

SEQ ID NO: 42 is the amino acid sequence of the VK gene IGKV3-11*01.

SEQ ID NO: 43 is the amino acid sequence of the VK gene IGKV3-20*01.

SEQ ID NO: 44 is the amino acid sequence for the wild type clade B HXBc2 core gp120.

SEQ ID NO: 45 is the amino acid sequence for the wild type clade A/E 93TH057 core gp120.

SEQ ID NO: 46 is the amino acid sequence of aV5 region of a gp120.

SEQ ID NOs: 47-58 are the amino acids sequences of 2F5 CDR H3 loop mutants.

SEQ ID NO: 59 is the amino acid sequence of a V1/V2 trim sequence of gp120 from HIV

SEQ ID NO: 60 is the nucleic acid sequence of VRC01 ImmunoAdhesin LH.

SEQ ID NOs: 61-759 are nucleic acid sequence of the heavy chains of VRC01 and VRC03-like antibodies.

SEQ ID NOs: 760-1459 are amino acid sequence of the heavy chains of VRC01 and VRC03-like antibodies.

DETAILED DESCRIPTION I. Terms

Unless otherwise noted, technical terms are used according to conventional usage. Definitions of common terms in molecular biology can be found in Benjamin Lewin, Genes V, published by Oxford University Press, 1994 (ISBN 0-19-854287-9); Kendrew et al. (eds.), The Encyclopedia of Molecular Biology, published by Blackwell Science Ltd., 1994 (ISBN 0-632-02182-9); and Robert A. Meyers (ed.), Molecular Biology and Biotechnology: a Comprehensive Desk Reference, published by VCH Publishers, Inc., 1995 (ISBN 1-56081-569-8). Terms describing protein structure and structural elements of proteins can be found in Creighton, Proteins, Structures and Molecular Properties, W.H. Freeman & Co., New York, 1993 (ISBN 0-717-7030) which is incorporated by reference herein in its entirety.

Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The singular terms “a,” “an,” and “the” include plural referents unless context clearly indicates otherwise. Similarly, the word “or” is intended to include “and” unless the context clearly indicates otherwise.

It is further to be understood that all base sizes or amino acid sizes, and all molecular weight or molecular mass values, given for nucleic acids or polypeptides are approximate, and are provided for descriptive purposes, unless otherwise indicated. Although many methods and materials similar or equivalent to those described herein can be used, particular suitable methods and materials are described below. In case of conflict, the present specification, including explanations of terms, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

To facilitate review of the various embodiments of this disclosure, the following explanations of terms are provided:

Administration: The introduction of a composition into a subject by a chosen route. Administration can be local or systemic. For example, if the chosen route is intravenous, the composition is administered by introducing the composition into a vein of the subject. In some examples a disclosed antibody specific for an HIV protein or polypeptide is administered to a subject.

Amino acid substitution: The replacement of one amino acid in peptide with a different amino acid.

Amplification: A technique that increases the number of copies of a nucleic acid molecule (such as an RNA or DNA). An example of amplification is the polymerase chain reaction, in which a biological sample is contacted with a pair of oligonucleotide primers, under conditions that allow for the hybridization of the primers to a nucleic acid template in the sample. The primers are extended under suitable conditions, dissociated from the template, and then re-annealed, extended, and dissociated to amplify the number of copies of the nucleic acid. The product of amplification can be characterized by electrophoresis, restriction endonuclease cleavage patterns, oligonucleotide hybridization or ligation, and/or nucleic acid sequencing using standard techniques. Other examples of amplification include strand displacement amplification, as disclosed in U.S. Pat. No. 5,744,311; transcription-free isothermal amplification, as disclosed in U.S. Pat. No. 6,033,881; repair chain reaction amplification, as disclosed in WO 90/01069; ligase chain reaction amplification, as disclosed in EP-A-320 308; gap filling ligase chain reaction amplification, as disclosed in U.S. Pat. No. 5,427,930; and NASBA™ RNA transcription-free amplification, as disclosed in U.S. Pat. No. 6,025,134.

Animal: Living multi-cellular vertebrate organisms, a category that includes, for example, mammals and birds. The term mammal includes both human and non-human mammals. Similarly, the term “subject” includes both human and veterinary subjects.

Antibody: A polypeptide substantially encoded by an immunoglobulin gene or immunoglobulin genes, or antigen binding fragments thereof, which specifically binds and recognizes an analyte (antigen) such as gp120, or gp41 or an antigenic fragment of gp120 or gp41. Immunoglobulin genes include the kappa, lambda, alpha, gamma, delta, epsilon and mu constant region genes, as well as the myriad immunoglobulin variable region genes.

Antibodies exist, for example as intact immunoglobulins and as a number of well characterized fragments produced by digestion with various peptidases. For instance, Fabs, Fvs, and single-chain Fvs (scFvs) that specifically bind to gp120 or fragments of gp120 would be gp120-specific binding agents. Similarly, Fabs, Fvs, scFvs that specifically bind to gp41 or fragments of gp41 would be gp41-specific binding agents. A scFv protein is a fusion protein in which a light chain variable region of an immunoglobulin and a heavy chain variable region of an immunoglobulin are bound by a linker, while in dsFvs, the chains have been mutated to introduce a disulfide bond to stabilize the association of the chains. The term also includes genetically engineered forms such as chimeric antibodies (such as humanized murine antibodies), heteroconjugate antibodies such as bispecific antibodies). See also, Pierce Catalog and Handbook, 1994-1995 (Pierce Chemical Co., Rockford, Ill.); Kuby, J., Immunology, 3^(rd) Ed., W.H. Freeman & Co., New York, 1997.

Antibody fragments are defined as follows: (1) Fab, the fragment which contains a monovalent antigen-binding fragment of an antibody molecule produced by digestion of whole antibody with the enzyme papain to yield an intact light chain and a portion of one heavy chain; (2) Fab′, the fragment of an antibody molecule obtained by treating whole antibody with pepsin, followed by reduction, to yield an intact light chain and a portion of the heavy chain; two Fab′ fragments are obtained per antibody molecule; (3) (Fab′)₂, the fragment of the antibody obtained by treating whole antibody with the enzyme pepsin without subsequent reduction; (4) F(ab′)₂, a dimer of two Fab′ fragments held together by two disulfide bonds; (5) Fv, a genetically engineered fragment containing the variable region of the light chain and the variable region of the heavy chain expressed as two chains; and (6) single chain antibody (“SCA”), a genetically engineered molecule containing the variable region of the light chain, the variable region of the heavy chain, linked by a suitable polypeptide linker as a genetically fused single chain molecule. The term “antibody,” as used herein, also includes antibody fragments either produced by the modification of whole antibodies or those synthesized de novo using recombinant DNA methodologies.

Typically, a naturally occurring immunoglobulin has heavy (H) chains and light (L) chains interconnected by disulfide bonds. There are two types of light chain, lambda (λ) and kappa (κ). There are five main heavy chain classes (or isotypes) which determine the functional activity of an antibody molecule: IgM, IgD, IgG, IgA and IgE.

Each heavy and light chain contains a constant region and a variable region (the regions are also known as “domains”). In combination, the heavy and the light chain variable regions specifically bind the antigen. Light and heavy chain variable regions contain a “framework” region interrupted by three hypervariable regions, also called “complementarity-determining regions” or “CDRs.” The extent of the framework region and CDRs have been defined (see, Kabat et al., Sequences of Proteins of Immunological Interest, U.S. Department of Health and Human Services, 1991, which is hereby incorporated by reference in its entirety). Thus one of ordinary skill in the art will recognize the numbering of the residues in the disclosed antibodies is made with reference to the Kabat or Immunogenetics (IMGT) convention. The Kabat database is now maintained online. The sequences of the framework regions of different light or heavy chains are relatively conserved within a species. The framework region of an antibody, that is the combined framework regions of the constituent light and heavy chains, serves to position and align the CDRs in three-dimensional space.

The CDRs are primarily responsible for binding to an epitope of an antigen. The CDRs of each chain are typically referred to as CDR1, CDR2, and CDR3, numbered sequentially starting from the N-terminus, and are also typically identified by the chain in which the particular CDR is located. Thus, a V_(H) CDR3 is located in the variable domain of the heavy chain of the antibody in which it is found, whereas a V_(L) CDR1 is the CDR1 from the variable domain of the light chain of the antibody in which it is found. Light chain CDRs are sometimes referred to as CDR L1, CDR L2, and CDR L3. Heavy chain CDRs are sometimes referred to as CDR H1, CDR H2, and CDR H3.

References to “V_(H)” or “VH” refer to the variable region of an immunoglobulin heavy chain, including that of an antibody fragment, such as Fv, scFv, dsFv or Fab. References to “V_(L)” or “VL” refer to the variable region of an immunoglobulin light chain, including that of an Fv, scFv, dsFv or Fab.

A “monoclonal antibody” is an antibody produced by a single clone of B-lymphocytes or by a cell into which the light and heavy chain genes of a single antibody have been transfected. Monoclonal antibodies are produced by methods known to those of skill in the art, for instance by making hybrid antibody-forming cells from a fusion of myeloma cells with immune spleen cells. These fused cells and their progeny are termed “hybridomas.” Monoclonal antibodies include humanized monoclonal antibodies. In some examples monoclonal antibodies are isolated from a subject. The amino acid sequences of such isolated monoclonal antibodies can be determined.

A “humanized” immunoglobulin is an immunoglobulin including a human framework region and one or more CDRs from a non-human (such as a mouse, rat, or synthetic) immunoglobulin. The non-human immunoglobulin providing the CDRs is termed a “donor,” and the human immunoglobulin providing the framework is termed an “acceptor.” In one embodiment, all the CDRs are from the donor immunoglobulin in a humanized immunoglobulin. Constant regions need not be present, but if they are, they must be substantially identical to human immunoglobulin constant regions, such as at least about 85-90%, such as about 95% or more identical. Hence, all parts of a humanized immunoglobulin, except possibly the CDRs, are substantially identical to corresponding parts of natural human immunoglobulin sequences. A “humanized antibody” is an antibody comprising a humanized light chain and a humanized heavy chain immunoglobulin. A humanized antibody binds to the same antigen as the donor antibody that provides the CDRs. The acceptor framework of a humanized immunoglobulin or antibody may have a limited number of substitutions by amino acids taken from the donor framework. Humanized or other monoclonal antibodies can have additional conservative amino acid substitutions which have substantially no effect on antigen binding or other immunoglobulin functions. Humanized immunoglobulins can be constructed by means of genetic engineering (for example, see U.S. Pat. No. 5,585,089).

Antigen: A compound, composition, or substance that can stimulate the production of antibodies or a T cell response in an animal, including compositions that are injected or absorbed into an animal. An antigen reacts with the products of specific humoral or cellular immunity, including those induced by heterologous antigens, such as the disclosed antigens. “Epitope” or “antigenic determinant” refers to the region of an antigen to which B and/or T cells respond. In one embodiment, T cells respond to the epitope, when the epitope is presented in conjunction with an MHC molecule. Epitopes can be formed both from contiguous amino acids or noncontiguous amino acids juxtaposed by tertiary folding of a protein. Epitopes formed from contiguous amino acids are typically retained on exposure to denaturing solvents whereas epitopes formed by tertiary folding are typically lost on treatment with denaturing solvents. An epitope typically includes at least 3, and more usually, at least 5, about 9, or about 8-10 amino acids in a unique spatial conformation. Methods of determining spatial conformation of epitopes include, for example, x-ray crystallography and nuclear magnetic resonance.

Examples of antigens include, but are not limited to, peptides, lipids, polysaccharides, and nucleic acids containing antigenic determinants, such as those recognized by an immune cell. In some examples, antigens include peptides derived from a pathogen of interest. Exemplary pathogens include bacteria, fungi, viruses and parasites. In specific examples, an antigen is derived from HIV, such as a gp120 polypeptide or antigenic fragment thereof, such as a gp120 outer domain or fragment thereof. In other examples an antigen a gp41 polypeptide derived from HIV or antigenic fragment thereof.

A “target epitope” is a specific epitope on an antigen that specifically binds a antibody of interest, such as a monoclonal antibody. In some examples, a target epitope includes the amino acid residues that contact the antibody of interest, such that the target epitope can be selected by the amino acid residues determined to be in contact with the antibody of interest.

Antigenic surface: A surface of a molecule, for example a protein such as a gp120 protein or polypeptide, capable of eliciting an immune response. An antigenic surface includes the defining features of that surface, for example the three-dimensional shape and the surface charge. An antigenic surface includes both surfaces that occur on gp120 polypeptides as well as surfaces of compounds that mimic the surface of a gp120 polypeptide (mimetics). In some examples, an antigenic surface include all or part of the surface of gp120 that binds to the CD4 receptor.

Atomic Coordinates or Structure coordinates: Mathematical coordinates derived from mathematical equations related to the patterns obtained on diffraction of a monochromatic beam of X-rays by the atoms (scattering centers) such as an antigen, or an antigen in complex with an antibody. In some examples that antigen can be gp120, a gp120:antibody complex, or combinations thereof in a crystal. In some examples that antigen can be gp41, a gp41:antibody complex, or combinations thereof in a crystal. The diffraction data are used to calculate an electron density map of the repeating unit of the crystal. The electron density maps are used to establish the positions of the individual atoms within the unit cell of the crystal. In one example, the term “structure coordinates” refers to Cartesian coordinates derived from mathematical equations related to the patterns obtained on diffraction of a monochromatic beam of X-rays, such as by the atoms of a gp120 in crystal form.

Those of ordinary skill in the art understand that a set of structure coordinates determined by X-ray crystallography is not without standard error. For the purpose of this disclosure, any set of structure coordinates that have a root mean square deviation of protein backbone atoms (N, Cα, C and 0) of less than about 1.0 Angstroms when superimposed, such as about 0.75, or about 0.5, or about 0.25 Angstroms, using backbone atoms, shall (in the absence of an explicit statement to the contrary) be considered identical.

Binding affinity: Affinity of an antibody or antigen binding fragment thereof for an antigen. In one embodiment, affinity is calculated by a modification of the Scatchard method described by Frankel et al., Mol. Immunol., 16:101-106, 1979. In another embodiment, binding affinity is measured by an antigen/antibody dissociation rate. In yet another embodiment, a high binding affinity is measured by a competition radioimmunoassay. In several examples, a high binding affinity is at least about 1×10⁻⁸ M. In other embodiments, a high binding affinity is at least about 1.5×10⁻⁸, at least about 2.0×10⁻⁸, at least about 2.5×10⁻⁸, at least about 3.0×10⁻⁸, at least about 3.5×10⁻⁸, at least about 4.0×10⁻⁸, at least about 4.5×10⁻⁸, or at least about 5.0×10⁻⁸ M.

CD4: Cluster of differentiation factor 4 polypeptide; a T-cell surface protein that mediates interaction with the MHC class II molecule. CD4 also serves as the primary receptor site for HIV on T-cells during HIV-I infection. CD4 is known to bind to gp120 from HIV. The known sequence of the CD4 precursor has a hydrophobic signal peptide, an extracellular region of approximately 370 amino acids, a highly hydrophobic stretch with significant identity to the membrane-spanning domain of the class II MHC beta chain, and a highly charged intracellular sequence of 40 resides (Maddon, Cell 42:93, 1985).

The term “CD4” includes polypeptide molecules that are derived from CD4 include fragments of CD4, generated either by chemical (for example enzymatic) digestion or genetic engineering means. Such a fragment may be one or more entire CD4 protein domains. The extracellular domain of CD4 consists of four contiguous immunoglobulin-like regions (D1, D2, D3, and D4, see Sakihama et al., Proc. Natl. Acad. Sci. 92:6444, 1995; U.S. Pat. No. 6,117,655), and amino acids 1 to 183 have been shown to be involved in gp120 binding. For instance, a binding molecule or binding domain derived from CD4 would comprise a sufficient portion of the CD4 protein to mediate specific and functional interaction between the binding fragment and a native or viral binding site of CD4. One such binding fragment includes both the D1 and D2 extracellular domains of CD4 (D1D2 is also a fragment of soluble CD4 or sCD4 which is comprised of D1 D2 D3 and D4), although smaller fragments may also provide specific and functional CD4-like binding. The gp120-binding site has been mapped to D1 of CD4.

CD4 polypeptides also include “CD4-derived molecules” which encompasses analogs (non-protein organic molecules), derivatives (chemically functionalized protein molecules obtained starting with the disclosed protein sequences) or mimetics (three-dimensionally similar chemicals) of the native CD4 structure, as well as proteins sequence variants or genetic alleles that maintain the ability to functionally bind to a target molecule.

CD4BS antibodies: Antibodies that bind to or substantially overlap the CD4 binding surface of a gp120 polypeptide. The antibodies interfere with or prevent CD4 from binding to a gp120 polypeptide.

CD4i antibodies: Antibodies that bind to a conformation of gp120 induced by CD4 binding.

Chimeric antibody: An antibody which includes sequences derived from two different antibodies, which typically are of different species. In some examples, a chimeric antibody includes one or more CDRs and/or framework regions from one human antibody and CDRs and/or framework regions from another human antibody.

Contacting: Placement in direct physical association; includes both in solid and liquid form, which can take place either in vivo or in vitro. Contacting includes contact between one molecule and another molecule, for example the amino acid on the surface of one polypeptide, such as an antigen, that contacts another polypeptide, such as an antibody. Contacting can also include contacting a cell for example by placing an antibody in direct physical association with a cell.

Computer readable media: Any medium or media, which can be read and accessed directly by a computer, so that the media is suitable for use in a computer system. Such media include, but are not limited to: magnetic storage media such as floppy discs, hard disc storage medium and magnetic tape; optical storage media such as optical discs or CD-ROM; electrical storage media such as RAM and ROM; and hybrids of these categories such as magnetic/optical storage media.

Computer system: Hardware that can be used to analyze atomic coordinate data and/or design an antigen using atomic coordinate data. The minimum hardware of a computer-based system typically comprises a central processing unit (CPU), an input device, for example a mouse, keyboard, and the like, an output device, and a data storage device. Desirably a monitor is provided to visualize structure data. The data storage device may be RAM or other means for accessing computer readable. Examples of such systems are microcomputer workstations available from Silicon Graphics Incorporated and Sun Microsystems running Unix based Windows NT or IBM OS/2 operating systems.

Epitope: An antigenic determinant. These are particular chemical groups or peptide sequences on a molecule that are antigenic, i.e. that elicit a specific immune response. An antibody specifically binds a particular antigenic epitope on a polypeptide. In some examples a disclosed antibody specifically binds to an epitope on the surface of gp120 from HIV. In some examples a disclosed antibody specifically binds to an epitope on the surface of gp41 from HIV.

Epitope Scaffold: Refers to a heterologous protein that is engrafted with a foreign epitope of interest on its surface. Transplantation of the epitope is performed computationally in a manner that preserves its relevant structure and conformation. Mutations within the acceptor scaffold are made in order to accommodate the epitope graft. The graft can be modified to represent the sequences of different clades and strains.

Framework Region: Amino acid sequences interposed between CDRs. Includes variable light and variable heavy framework regions. The framework regions serve to hold the CDRs in an appropriate orientation for antigen binding.

Fc polypeptide: The polypeptide comprising the constant region of an antibody excluding the first constant region immunoglobulin domain. Fc region generally refers to the last two constant region immunoglobulin domains of IgA, IgD, and IgG, and the last three constant region immunoglobulin domains of IgE and IgM. An Fc region may also include part or all of the flexible hinge N-terminal to these domains. For IgA and IgM, an Fc region may or may not comprise the tailpiece, and may or may not be bound by the J chain. For IgG, the Fc region comprises immunoglobulin domains Cgamma2 and Cgamma3 (Cγ2 and Cγ3) and the lower part of the hinge between Cgamma1 (Cγ1) and Cγ2. Although the boundaries of the Fc region may vary, the human IgG heavy chain Fc region is usually defined to comprise residues C226 or P230 to its carboxyl-terminus, wherein the numbering is according to the EU index as in Kabat. For IgA, the Fc region comprises immunoglobulin domains Calpha2 and Calpha3 (Cα2 and Cα3) and the lower part of the hinge between Calpha1 (Cα1) and Cα2. Encompassed within the definition of the Fc region are functionally equivalent analogs and variants of the Fc region. A functionally equivalent analog of the Fc region may be a variant Fc region, comprising one or more amino acid modifications relative to the wild-type or naturally existing Fc region. Variant Fc regions will possess at least 50% homology with a naturally existing Fc region, such as about 80%, and about 90%, or at least about 95% homology. Functionally equivalent analogs of the Fc region may comprise one or more amino acid residues added to or deleted from the N- or C-termini of the protein, such as no more than 30 or no more than 10 additions and/or deletions. Functionally equivalent analogs of the Fc region include Fc regions operably linked to a fusion partner. Functionally equivalent analogs of the Fc region must comprise the majority of all of the Ig domains that compose Fc region as defined above; for example IgG and IgA Fc regions as defined herein must comprise the majority of the sequence encoding CH₂ and the majority of the sequence encoding CH₃. Thus, the CH₂ domain on its own, or the CH₃ domain on its own, are not considered Fc region. The Fc region may refer to this region in isolation, or this region in the context of an Fc fusion polypeptide (immunoadhesin, see below).

Furin: A calcium dependent serine endoprotease that cleaves precursor proteins at paired basic amino acid processing sites. In vivo, substrates of furin include proparathyroid hormone, proablumin, and von Willebrand factor. Furin can also cleave HIV envelope protein gp160 into gp120 and gp41. Furin cleaves proteins just downstream of a basic amino acid target sequence (canonically, Arg-X-(Arg/Lys)-Arg′). Thus, this amino acid sequence is a furin cleavage site.

gp41: A HIV protein that contains a transmembrane domain and remains in a trimeric configuration; it interacts with gp120 in a non-covalent manner. The envelope protein of HIV-1 is initially synthesized as a longer precursor protein of 845-870 amino acids in size, designated gp160. gp160 forms a homotrimer and undergoes glycosylation within the Golgi apparatus. In vivo, it is then cleaved by a cellular protease into gp120 and gp41. The amino acid sequence of an example of gp41 is set forth in GENBANK® Accession No. CAD20975 (as available on Oct. 16, 2009) which is incorporated by reference herein. It is understood that the sequence of gp41 can vary from that given in GENBANK® Accession No. CAD20975. gp41 contains a transmembrane domain and typically remains in a trimeric configuration; it interacts with gp120 in a non-covalent manner.

gp120: An envelope protein from Human Immunodeficiency Virus (HIV). This envelope protein is initially synthesized as a longer precursor protein of 845-870 amino acids in size, designated gp160. gp160 is cleaved by a cellular protease into gp120 and gp41. gp120 contains most of the external, surface-exposed, domains of the HIV envelope glycoprotein complex, and it is gp120 which binds both to cellular CD4 receptors and to cellular chemokine receptors (such as CCR5).

The mature gp120 wildtype polypeptides have about 500 amino acids in the primary sequence. gp120 is heavily N-glycosylated giving rise to an apparent molecular weight of 120 kD. The polypeptide is comprised of five conserved regions (C1-C5) and five regions of high variability (V1-V5). Exemplary sequence of wt gp120 polypeptides are shown on GENBANK®, for example accession numbers AAB05604 and AAD12142 (as available on Oct. 16, 2009), incorporated by reference herein. It is understood that there are numerous variation in the sequence of gp120 from what is given in GENBANK®, for example accession numbers AAB05604 and AAD12142, and that these variants are skill recognized in the art as gp120.

The gp120 core has a molecular structure, which includes two domains: an “inner” domain (which faces gp41) and an “outer” domain (which is mostly exposed on the surface of the oligomeric envelope glycoprotein complex). The two gp120 domains are separated by a “bridging sheet” that is not part of either domain. The gp120 core comprises 25 beta strands, 5 alpha helices, and 10 defined loop segments.

The third variable region referred to herein as the V3 loop is a loop of about 35 amino acids critical for the binding of the co-receptor and determination of which of the co-receptors will bind. In certain examples the V3 loop comprises residues 296-331.

The numbering used in gp120 polypeptides disclosed herein is relative to the HXB2 numbering scheme as set forth in Numbering Positions in HIV Relative to HXB2CG Bette Korber et al., Human Retroviruses and AIDS 1998: A Compilation and Analysis of Nucleic Acid and Amino Acid Sequences. Korber B, Kuiken C L, Foley B, Hahn B, McCutchan F, Mellors J W, and Sodroski J, Eds. Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, N. Mex. which is incorporated by reference herein in its entirety.

Host cells: Cells in which a vector can be propagated and its DNA expressed, for example a disclosed antibody can be expressed in a host cell. The cell may be prokaryotic or eukaryotic. The term also includes any progeny of the subject host cell. It is understood that all progeny may not be identical to the parental cell since there may be mutations that occur during replication. However, such progeny are included when the term “host cell” is used.

Immunoadhesin: A molecular fusion of a protein with the Fc region of an immunoglobulin, wherein the immunogloblin retains specific properties, such as Fc receptor binding and increased half-life. An Fc fusion combines the Fc region of an immunoglobulin with a fusion partner, which in general can be any protein, polypeptide, peptide, or small molecule. In one example, and immunoadhesin includes the hinge, CH₂, and CH₃ domains of the immunoglobulin gamma 1 heavy chain constant region. In another example, the immunoadhesin includes the CH₂, and CH₃ domains of an IgG.

Immunological Probe: A molecule that can be used for selection of antibodies from sera which are directed against a specific epitope, including from human patient sera. The epitope scaffolds, along with related point mutants, can be used as immunological probes in both positive and negative selection of antibodies against the epitope graft. In some examples immunological probes are engineered variants of gp120.

Immunologically reactive conditions: Includes reference to conditions which allow an antibody raised against a particular epitope to bind to that epitope to a detectably greater degree than, and/or to the substantial exclusion of, binding to substantially all other epitopes. Immunologically reactive conditions are dependent upon the format of the antibody binding reaction and typically are those utilized in immunoassay protocols or those conditions encountered in vivo. See Harlow & Lane, supra, for a description of immunoassay formats and conditions. The immunologically reactive conditions employed in the methods are “physiological conditions” which include reference to conditions (e.g., temperature, osmolarity, pH) that are typical inside a living mammal or a mammalian cell. While it is recognized that some organs are subject to extreme conditions, the intra-organismal and intracellular environment normally lies around pH 7 (e.g., from pH 6.0 to pH 8.0, more typically pH 6.5 to 7.5), contains water as the predominant solvent, and exists at a temperature above 0° C. and below 50° C. Osmolarity is within the range that is supportive of cell viability and proliferation.

IgA: A polypeptide belonging to the class of antibodies that are substantially encoded by a recognized immunoglobulin alpha gene. In humans, this class or isotype comprises IgA₁ and IgA₂. IgA antibodies can exist as monomers, polymers (referred to as pIgA) of predominantly dimeric form, and secretory IgA. The constant chain of wild-type IgA contains an 18-amino-acid extension at its C-terminus called the tail piece (tp). Polymeric IgA is secreted by plasma cells with a 15-kDa peptide called the J chain linking two monomers of IgA through the conserved cysteine residue in the tail piece.

IgG: A polypeptide belonging to the class or isotype of antibodies that are substantially encoded by a recognized immunoglobulin gamma gene. In humans, this class comprises IgG₁, IgG₂, IgG₃, and IgG₄. In mice, this class comprises IgG₁, IgG_(2a), IgG_(2b), IgG₃.

Inhibiting or treating a disease: Inhibiting the full development of a disease or condition, for example, in a subject who is at risk for a disease such as acquired immunodeficiency syndrome (AIDS). “Treatment” refers to a therapeutic intervention that ameliorates a sign or symptom of a disease or pathological condition after it has begun to develop. The term “ameliorating,” with reference to a disease or pathological condition, refers to any observable beneficial effect of the treatment. The beneficial effect can be evidenced, for example, by a delayed onset of clinical symptoms of the disease in a susceptible subject, a reduction in severity of some or all clinical symptoms of the disease, a slower progression of the disease, a reduction in the viral load, an improvement in the overall health or well-being of the subject, or by other parameters well known in the art that are specific to the particular disease. A “prophylactic” treatment is a treatment administered to a subject who does not exhibit signs of a disease or exhibits only early signs for the purpose of decreasing the risk of developing pathology.

Isolated: An “isolated” biological component (such as a cell, for example a Bcell, a nucleic acid, peptide, protein or antibody) has been substantially separated, produced apart from, or purified away from other biological components in the cell of the organism in which the component naturally occurs, such as, other chromosomal and extrachromosomal DNA and RNA, and proteins. Nucleic acids, peptides and proteins which have been “isolated” thus include nucleic acids and proteins purified by standard purification methods. The term also embraces nucleic acids, peptides, and proteins prepared by recombinant expression in a host cell as well as chemically synthesized nucleic acids. In some examples an antibody, such as an antibody specific for gp120 can be isolated, for example isolated from a subject infected with HIV.

In silico: A process performed virtually within a computer. For example, using a computer, a virtual compound can be screened for surface similarity or conversely surface complementarity to a virtual representation of the atomic positions at least a portion of a gp120 polypeptide, a gp120 polypeptide in complex with an antibody, a gp41 polypeptide, or a pg41 polypeptide in complex with an antibody.

K_(d): The dissociation constant for a given interaction, such as a polypeptide ligand interaction or an antibody antigen interaction. For example, for the bimolecular interaction of an antibody (such as VRC01, VRC02, or VRC03) and an antigen (such as gp120) it is the concentration of the individual components of the bimolecular interaction divided by the concentration of the complex.

Label: A detectable compound or composition that is conjugated directly or indirectly to another molecule, such as an antibody or a protein, to facilitate detection of that molecule. Specific, non-limiting examples of labels include fluorescent tags, enzymatic linkages, and radioactive isotopes. In some examples, a disclosed antibody as labeled.

Neutralizing antibody: An antibody which reduces the infectious titer of an infectious agent by binding to a specific antigen on the infectious agent. In some examples the infectious agent is a virus. In some examples, an antibody that is specific for gp120 neutralizes the infectious titer of HIV.

Nucleic acid: A polymer composed of nucleotide units (ribonucleotides, deoxyribonucleotides, related naturally occurring structural variants, and synthetic non-naturally occurring analogs thereof) linked via phosphodiester bonds, related naturally occurring structural variants, and synthetic non-naturally occurring analogs thereof. Thus, the term includes nucleotide polymers in which the nucleotides and the linkages between them include non-naturally occurring synthetic analogs, such as, for example and without limitation, phosphorothioates, phosphoramidates, methyl phosphonates, chiral-methyl phosphonates, 2-O-methyl ribonucleotides, peptide-nucleic acids (PNAs), and the like. Such polynucleotides can be synthesized, for example, using an automated DNA synthesizer. The term “oligonucleotide” typically refers to short polynucleotides, generally no greater than about 50 nucleotides. It will be understood that when a nucleotide sequence is represented by a DNA sequence (i.e., A, T, G, C), this also includes an RNA sequence (i.e., A, U, G, C) in which “U” replaces “T.”

Conventional notation is used herein to describe nucleotide sequences: the left-hand end of a single-stranded nucleotide sequence is the 5′-end; the left-hand direction of a double-stranded nucleotide sequence is referred to as the 5′-direction. The direction of 5′ to 3′ addition of nucleotides to nascent RNA transcripts is referred to as the transcription direction. The DNA strand having the same sequence as an mRNA is referred to as the “coding strand;” sequences on the DNA strand having the same sequence as an mRNA transcribed from that DNA and which are located 5′ to the 5′-end of the RNA transcript are referred to as “upstream sequences;” sequences on the DNA strand having the same sequence as the RNA and which are 3′ to the 3′ end of the coding RNA transcript are referred to as “downstream sequences.”

“cDNA” refers to a DNA that is complementary or identical to an mRNA, in either single stranded or double stranded form.

“Encoding” refers to the inherent property of specific sequences of nucleotides in a polynucleotide, such as a gene, a cDNA, or an mRNA, to serve as templates for synthesis of other polymers and macromolecules in biological processes having either a defined sequence of nucleotides (i.e., rRNA, tRNA and mRNA) or a defined sequence of amino acids and the biological properties resulting therefrom. Thus, a gene encodes a protein if transcription and translation of mRNA produced by that gene produces the protein in a cell or other biological system. Both the coding strand, the nucleotide sequence of which is identical to the mRNA sequence and is usually provided in sequence listings, and non-coding strand, used as the template for transcription, of a gene or cDNA can be referred to as encoding the protein or other product of that gene or cDNA. Unless otherwise specified, a “nucleotide sequence encoding an amino acid sequence” includes all nucleotide sequences that are degenerate versions of each other and that encode the same amino acid sequence. Nucleotide sequences that encode proteins and RNA may include introns.

“Recombinant nucleic acid” refers to a nucleic acid having nucleotide sequences that are not naturally joined together. This includes nucleic acid vectors comprising an amplified or assembled nucleic acid which can be used to transform a suitable host cell. A host cell that comprises the recombinant nucleic acid is referred to as a “recombinant host cell.” The gene is then expressed in the recombinant host cell to produce, e.g., a “recombinant polypeptide.” A recombinant nucleic acid may serve a non-coding function (e.g., promoter, origin of replication, ribosome-binding site, etc.) as well.

A first sequence is an “antisense” with respect to a second sequence if a polynucleotide whose sequence is the first sequence specifically hybridizes with a polynucleotide whose sequence is the second sequence.

Terms used to describe sequence relationships between two or more nucleotide sequences or amino acid sequences include “reference sequence,” “selected from,” “comparison window,” “identical,” “percentage of sequence identity,” “substantially identical,” “complementary,” and “substantially complementary.”

For sequence comparison of nucleic acid sequences, typically one sequence acts as a reference sequence, to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are entered into a computer, subsequence coordinates are designated, if necessary, and sequence algorithm program parameters are designated. Default program parameters are used. Methods of alignment of sequences for comparison are well known in the art. Optimal alignment of sequences for comparison can be conducted, e.g., by the local homology algorithm of Smith & Waterman, Adv. Appl. Math. 2:482, 1981, by the homology alignment algorithm of Needleman & Wunsch, J. Mol. Biol. 48:443, 1970, by the search for similarity method of Pearson & Lipman, Proc. Nat'l. Acad. Sci. USA 85:2444, 1988, by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wis.), or by manual alignment and visual inspection (see, e.g., Current Protocols in Molecular Biology (Ausubel et al., eds 1995 supplement)).

One example of a useful algorithm is PILEUP. PILEUP uses a simplification of the progressive alignment method of Feng & Doolittle, J. Mol. Evol. 35:351-360, 1987. The method used is similar to the method described by Higgins & Sharp, CABIOS 5:151-153, 1989. Using PILEUP, a reference sequence is compared to other test sequences to determine the percent sequence identity relationship using the following parameters: default gap weight (3.00), default gap length weight (0.10), and weighted end gaps. PILEUP can be obtained from the GCG sequence analysis software package, e.g., version 7.0 (Devereaux et al., Nuc. Acids Res. 12:387-395, 1984.

Another example of algorithms that are suitable for determining percent sequence identity and sequence similarity are the BLAST and the BLAST 2.0 algorithm, which are described in Altschul et al., J. Mol. Biol. 215:403-410, 1990 and Altschul et al., Nucleic Acids Res. 25:3389-3402, 1977. Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information (ncbi.nlm.nih.gov). The BLASTN program (for nucleotide sequences) uses as defaults a word length (W) of 11, alignments (B) of 50, expectation (E) of 10, M=5, N=−4, and a comparison of both strands. The BLASTP program (for amino acid sequences) uses as defaults a word length (W) of 3, and expectation (E) of 10, and the BLOSUM62 scoring matrix (see Henikoff & Henikoff, Proc. Natl. Acad. Sci. USA 89:10915, 1989). An oligonucleotide is a linear polynucleotide sequence of up to about 100 nucleotide bases in length.

A polynucleotide or nucleic acid sequence refers to a polymeric form of nucleotide at least 10 bases in length. A recombinant polynucleotide includes a polynucleotide that is not immediately contiguous with both of the coding sequences with which it is immediately contiguous (one on the 5′ end and one on the 3′ end) in the naturally occurring genome of the organism from which it is derived. The term therefore includes, for example, a recombinant DNA which is incorporated into a vector; into an autonomously replicating plasmid or virus; or into the genomic DNA of a prokaryote or eukaryote, or which exists as a separate molecule (e.g., a cDNA) independent of other sequences. The nucleotides can be ribonucleotides, deoxyribonucleotides, or modified forms of either nucleotide. The term includes single- and double-stranded forms of DNA. A gp120 polynucleotide is a nucleic acid encoding a gp120 polypeptide.

Pharmaceutically acceptable carriers: The pharmaceutically acceptable carriers of use are conventional. Remington's Pharmaceutical Sciences, by E. W. Martin, Mack Publishing Co., Easton, Pa., 19th Edition, 1995, describes compositions and formulations suitable for pharmaceutical delivery of the antibodies herein disclosed.

In general, the nature of the carrier will depend on the particular mode of administration being employed. For instance, parenteral formulations usually comprise injectable fluids that include pharmaceutically and physiologically acceptable fluids such as water, physiological saline, balanced salt solutions, aqueous dextrose, glycerol or the like as a vehicle. For solid compositions (e.g., powder, pill, tablet, or capsule forms), conventional non-toxic solid carriers can include, for example, pharmaceutical grades of mannitol, lactose, starch, or magnesium stearate. In addition to biologically neutral carriers, pharmaceutical compositions to be administered can contain minor amounts of non-toxic auxiliary substances, such as wetting or emulsifying agents, preservatives, and pH buffering agents and the like, for example sodium acetate or sorbitan monolaurate.

Pharmaceutical agent: A chemical compound or composition capable of inducing a desired therapeutic or prophylactic effect when properly administered to a subject or a cell. In some examples a pharmaceutical agent includes one or more of the disclosed antibodies.

Polypeptide: Any chain of amino acids, regardless of length or post-translational modification (e.g., glycosylation or phosphorylation). In one embodiment, the polypeptide is gp120 polypeptide. In another embodiment, the polypeptide is gp41 polypeptide. In one embodiment, the polypeptide is a disclosed antibody or a fragment thereof. A “residue” refers to an amino acid or amino acid mimetic incorporated in a polypeptide by an amide bond or amide bond mimetic. A polypeptide has an amino terminal (N-terminal) end and a carboxy terminal end.

Purified: The term purified does not require absolute purity; rather, it is intended as a relative term. Thus, for example, a purified peptide preparation is one in which the peptide or protein (such as an antibody) is more enriched than the peptide or protein is in its natural environment within a cell. In one embodiment, a preparation is purified such that the protein or peptide represents at least 50% of the total peptide or protein content of the preparation.

Recombinant: A recombinant nucleic acid is one that has a sequence that is not naturally occurring or has a sequence that is made by an artificial combination of two otherwise separated segments of sequence. This artificial combination is often accomplished by chemical synthesis or, more commonly, by the artificial manipulation of isolated segments of nucleic acids, e.g., by genetic engineering techniques.

Sequence identity: The similarity between amino acid sequences is expressed in terms of the similarity between the sequences, otherwise referred to as sequence identity. Sequence identity is frequently measured in terms of percentage identity (or similarity or homology); the higher the percentage, the more similar the two sequences are. Homologs or variants of a polypeptide will possess a relatively high degree of sequence identity when aligned using standard methods.

Methods of alignment of sequences for comparison are well known in the art. Various programs and alignment algorithms are described in: Smith and Waterman, Adv. Appl. Math. 2:482, 1981; Needleman and Wunsch, J. Mol. Biol. 48:443, 1970; Pearson and Lipman, Proc. Natl. Acad. Sci. U.S.A. 85:2444, 1988; Higgins and Sharp, Gene 73:237, 1988; Higgins and Sharp, CABIOS 5:151, 1989; Corpet et al., Nucleic Acids Research 16:10881, 1988; and Pearson and Lipman, Proc. Natl. Acad. Sci. U.S.A. 85:2444, 1988. Altschul et al., Nature Genet. 6:119, 1994, presents a detailed consideration of sequence alignment methods and homology calculations.

The NCBI Basic Local Alignment Search Tool (BLAST) (Altschul et al., J. Mol. Biol. 215:403, 1990) is available from several sources, including the National Center for Biotechnology Information (NCBI, Bethesda, Md.) and on the internet, for use in connection with the sequence analysis programs blastp, blastn, blastx, tblastn and tblastx. A description of how to determine sequence identity using this program is available on the NCBI website on the internet.

Homologs and variants of a V_(L) or a V_(H) of an antibody that specifically binds a polypeptide are typically characterized by possession of at least about 75%, for example at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity counted over the full length alignment with the amino acid sequence of interest. Proteins with even greater similarity to the reference sequences will show increasing percentage identities when assessed by this method, such as at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% sequence identity. When less than the entire sequence is being compared for sequence identity, homologs and variants will typically possess at least 80% sequence identity over short windows of 10-20 amino acids, and may possess sequence identities of at least 85% or at least 90% or 95% depending on their similarity to the reference sequence. Methods for determining sequence identity over such short windows are available at the NCBI website on the internet. One of skill in the art will appreciate that these sequence identity ranges are provided for guidance only; it is entirely possible that strongly significant homologs could be obtained that fall outside of the ranges provided.

Specifically bind: When referring to an antibody, refers to a binding reaction which determines the presence of a target protein, peptide, or polysaccharide in the presence of a heterogeneous population of proteins and other biologics. Thus, under designated conditions, an antibody binds preferentially to a particular target protein, peptide or polysaccharide (such as an antigen present on the surface of a pathogen, for example gp120) and do not bind in a significant amount to other proteins or polysaccharides present in the sample or subject. Specific binding can be determined by methods known in the art. With reference to an antibody antigen complex, specific binding of the antigen and antibody has a K_(d) of less than about 10⁻⁶ Molar, such as less than about 10⁻⁶ Molar, 10⁻⁷ Molar, 10⁻⁸ Molar, 10⁻⁹, or even less than about 10⁻¹⁰ Molar.

Therapeutic agent: Used in a generic sense, it includes treating agents, prophylactic agents, and replacement agents.

Therapeutically effective amount: A quantity of a specific substance, such as a disclosed antibody, sufficient to achieve a desired effect in a subject being treated. For instance, this can be the amount necessary to inhibit HIV replication or treat AIDS. In several embodiments, a therapeutically effective amount is the amount necessary to reduce a sign or symptom of AIDS, and/or to decrease viral titer in a subject. When administered to a subject, a dosage will generally be used that will achieve target tissue concentrations that has been shown to achieve a desired in vitro effect.

T Cell: A white blood cell critical to the immune response. T cells include, but are not limited to, CD4⁺ T cells and CD8⁺ T cells. A CD4⁺ T lymphocyte is an immune cell that carries a marker on its surface known as “cluster of differentiation 4” (CD4). These cells, also known as helper T cells, help orchestrate the immune response, including antibody responses as well as killer T cell responses. CD8⁺ T cells carry the “cluster of differentiation 8” (CD8) marker. In one embodiment, a CD8 T cells is a cytotoxic T lymphocytes. In another embodiment, a CD8 cell is a suppressor T cell.

Vector: A nucleic acid molecule as introduced into a host cell, thereby producing a transformed host cell. A vector may include nucleic acid sequences that permit it to replicate in a host cell, such as an origin of replication. A vector may also include one or more selectable marker genes and other genetic elements known in the art.

Virus: Microscopic infectious organism that reproduces inside living cells. A virus consists essentially of a core of a single nucleic acid surrounded by a protein coat, and has the ability to replicate only inside a living cell. “Viral replication” is the production of additional virus by the occurrence of at least one viral life cycle. A virus may subvert the host cells' normal functions, causing the cell to behave in a manner determined by the virus. For example, a viral infection may result in a cell producing a cytokine, or responding to a cytokine, when the uninfected cell does not normally do so.

“Retroviruses” are RNA viruses wherein the viral genome is RNA. When a host cell is infected with a retrovirus, the genomic RNA is reverse transcribed into a DNA intermediate which is integrated very efficiently into the chromosomal DNA of infected cells. The integrated DNA intermediate is referred to as a provirus. The term “lentivirus” is used in its conventional sense to describe a genus of viruses containing reverse transcriptase. The lentiviruses include the “immunodeficiency viruses” which include human immunodeficiency virus (HIV) type 1 and type 2 (HIV-I and HIV-II), simian immunodeficiency virus (SIV), and feline immunodeficiency virus (FIV).

HIV-I is a retrovirus that causes immunosuppression in humans (HIV disease), and leads to a disease complex known as the acquired immunodeficiency syndrome (AIDS). “HIV disease” refers to a well-recognized constellation of signs and symptoms (including the development of opportunistic infections) in persons who are infected by an HIV virus, as determined by antibody or western blot studies. Laboratory findings associated with this disease are a progressive decline in T cells.

II. Description of Several Embodiments

A. Neutralizing Monoclonal Antibodies

Isolated human monoclonal antibodies that specifically bind gp120 or gp41 are disclosed herein. Also disclosed herein are compositions including these human monoclonal antibodies and a pharmaceutically acceptable carrier. Nucleic acids encoding these antibodies, expression vectors comprising these nucleic acids, and isolated host cells that express the nucleic acids are also provided.

Compositions comprising the human monoclonal antibodies specific for gp120 or gp41 can be used for research, diagnostic and therapeutic purposes. For example, the human monoclonal antibodies disclosed herein can be used to diagnose or treat a subject having an HIV-1 infection and/or AIDS. For example, the antibodies can be used to determine HIV-1 titer in a subject. The antibodies disclosed herein also can be used to study the biology of the human immunodeficiency virus.

In some embodiments, the isolated human monoclonal antibody specifically binds gp120, and includes a heavy chain with amino acids 26-33 (CDR1), 51-58 (CDR2), and 97-110 (CDR3) of SEQ ID NO: 1. In specific examples, the heavy chain of the human monoclonal antibody includes SEQ ID NO: 1. In additional examples, the heavy chain of the monoclonal antibody includes SEQ ID NO: 3. In another example, the isolated human monoclonal antibody specifically binds gp120, and includes a heavy chain with amino acids 26-33 (CDR1), 51-58 (CDR2), and 97-110 (CDR3) of SEQ ID NO: 1 and the light chain of the antibody includes amino acids 27-30 (CDR1), 48-50 (CDR2), and 87-91 (CDR3) of SEQ ID NO: 2. In additional embodiments, the isolated human monoclonal antibody specifically binds gp120 and the light chain of the antibody includes amino acids 27-30 (CDR1), 48-50 (CDR2), and 87-91 (CDR3) of SEQ ID NO: 2. In specific examples, the light chain of the antibody includes SEQ ID NO: 2. In additional examples, the light chain of the antibody includes SEQ ID NO: 4.

In further embodiments, the isolated human monoclonal antibody specifically binds gp120, and includes a heavy chain with at most one, at most two, at most three or at most four amino acid substitutions in amino acids 26-33 (CDR1), 51-58 (CDR2), and 97-110 (CDR3) of SEQ ID NO: 1, and a light chain. In some embodiments, the antibody can include a heavy chain with at most one, at most two, at most three or at most four amino acid substitutions in amino acids in 26-33 (CDR1), 51-58 (CDR2), and 97-110 (CDR3) of SEQ ID NO: 1, and can include a light chain that includes amino acids 27-30 (CDR1), 48-50 (CDR2), and 87-91 (CDR3) of SEQ ID NO: 2. In some embodiments, the antibody can include a heavy chain with at most one, at most two, at most three or at most four amino acid substitutions amino acids in 26-33 (CDR1), 51-58 (CDR2), and 97-110 (CDR3) of SEQ ID NO: 1, and can include a light chain with at most one, at most two, at most three or at most four amino acid substitutions in amino acids 27-30 (CDR1), 48-50 (CDR2), and 87-91 (CDR3) of SEQ ID NO: 2.

The antibody can include a heavy chain with at most one, at most two, at most three or at most four amino acid substitutions amino acids in 26-33 (CDR1), 51-58 (CDR2), and 97-110 (CDR3) of SEQ ID NO: 1 and a light chain that can include SEQ ID NO: 2 or SEQ ID NO: 4. In some examples, these antibodies retain the binding affinity of the parental antibody (VRC01 or VRC02) for the antigenic epitope. Thus, in some examples, these antibodies have a KD of <3 nM for the antigenic epitope of gp120.

In another set of embodiments, the isolated human monoclonal antibody specifically binds gp120, and the light chain of the antibody includes at most one, at most two, at most three or at most four substitutions in amino acids 27-30 (CDR1), 48-50 (CDR2), and 87-91 (CDR3) of SEQ ID NO: 2. It should be noted that no more than three substitutions can be made in CDR2. The isolated monoclonal antibody can include a heavy chain that includes amino acids 26-33 (CDR1), 51-58 (CDR2), and 97-110 (CDR3) of SEQ ID NO: 1 and the light chain of the antibody can include at most one, at most two, at most three or at most four substitutions in amino acids 27-30 (CDR1), 48-50 (CDR2), and 87-91 (CDR3) of SEQ ID NO: 2. It should be noted that no more than three substitutions can be made in CDR2. The antibody can include a heavy chain including the amino acid sequence set forth as SEQ ID NO: 1 or SEQ ID NO: 3, and a light chain that includes SEQ ID NO: 2 with at most one, at most two, at most three or at most four substitutions in amino acids 27-30 (CDR1), 48-50 (CDR2), and 87-91 (CDR3) of SEQ ID NO: 2. It should be noted that no more than three substitutions can be made in CDR2. In some examples, these antibodies retain the binding affinity of the parental antibody (VRC01 or VRC02) for the antigenic epitope. Thus, in some examples, these antibodies have a K_(D) of <3 nM for the antigenic epitope of gp120.

In some embodiments, the isolated human monoclonal antibody specifically binds gp120, and includes a heavy chain with amino acids 26-35 (CDR1), 50-66 (CDR2), and 106-119 (CDR3) of SEQ ID NO: 27. In specific examples, the heavy chain of the human monoclonal antibody includes SEQ ID NO: 27. In another example, the isolated human monoclonal antibody specifically binds gp120, and includes a heavy chain with amino acids 26-35 (CDR1), 50-66 (CDR2), and 106-119 (CDR3) of SEQ ID NO: 27 and a light chain that includes amino acids 24-33 (CDR1), 49-55 (CDR2), and 88-92 (CDR3) of SEQ ID NO: 28.

In further embodiments, the isolated human monoclonal antibody specifically binds gp120, and includes a heavy chain with at most one, at most two, at most three or at most four amino acid substitutions in amino acids 26-35 (CDR1), 50-66 (CDR2), and 106-119 (CDR3) of SEQ ID NO: 27, and a light chain. The antibody can include a heavy chain with at most one, at most two, at most three or at most four amino acid substitutions amino acids in 26-35 (CDR1), 50-66 (CDR2), and 106-119 (CDR3) of SEQ ID NO: 27, and a light chain that includes amino acids 24-33 (CDR1), 49-55 (CDR2), and 88-92 (CDR3) of SEQ ID NO: 28. The antibody can include a heavy chain with at most one, at most two, at most three or at most four amino acid substitutions amino acids in 26-35 (CDR1), 50-66 (CDR2), and 106-119 (CDR3) of SEQ ID NO: 27 and the light chain of the antibody can include SEQ ID NO: 28. In some examples, these antibodies retain the binding affinity of the parental antibody (VRC03) for the antigenic epitope.

In another set of embodiments, the isolated human monoclonal antibody specifically binds gp120, and the light chain of the antibody includes at most one, at most two, at most three or at most four substitutions in amino acids 24-33 (CDR1), 49-55 (CDR2), and 88-92 (CDR3) of SEQ ID NO: 28. The isolated monoclonal antibody can include a heavy chain that includes 26-35 (CDR1), 50-66 (CDR2), and 106-119 (CDR3) of SEQ ID NO: 27 and a light chain that include at most one, at most two, at most three or at most four substitutions in amino acids 24-33 (CDR1), 49-55 (CDR2), and 88-92 (CDR3) of SEQ ID NO: 28. The antibody can include a heavy chain including the amino acid sequence set forth as SEQ ID NO: 27, and a light chain that includes at most one, at most two, at most three or at most four substitutions in amino acids 24-33 (CDR1), 49-55 (CDR2), and 88-92 (CDR3) of SEQ ID NO: 28. In some examples, these antibodies retain the binding affinity of the parental antibody (VRC03) for the antigenic epitope. In additional embodiments, the isolated human monoclonal antibody specifically binds gp120 and the light chain of the antibody includes amino acids 24-33 (CDR1), 49-55 (CDR2), and 88-92 (CDR3) of SEQ ID NO: 28. In specific examples, the light chain of the antibody includes SEQ ID NO: 28.

In some embodiments, the isolated human monoclonal antibody specifically binds gp120, and includes a heavy chain with CDR1, CDR2, and CDR3 of any one of SEQ ID NOs: 760-1459. In specific examples, the heavy chain of the human monoclonal antibody includes any one of SEQ ID NOs: 760-1459. In some embodiments, the isolated human monoclonal antibody specifically binds gp120, and includes a heavy chain with CDR1, CDR2, and CDR3 of SEQ ID NO: 1316. In specific examples, the heavy chain of the human monoclonal antibody includes the amino acids set forth as SEQ ID NO: 1316.

VRC01 and VRC03-like antibodies share unique binding site on the surface of gp120. Thus, in some embodiments, the antibody specifically binds to an epitope on the surface of gp120 that includes, residues 276, 278-283, 365-368, 371, 455-459, 461, 469, and 472-474 of gp120 or a subset or combination thereof (see FIGs. see FIGS. 83-91 and 93-97, the numbering of gp120 according to the HXBC2 convention is shown in FIG. 91). With reference to FIG. 91. VRC01 and VRC0-like antibodies bind to the epitope defined by residues

N₂₇₆.T₂₇₈NNAKT₂₈₃..S₃₆₅GGD₃₆₈..I₃₇₁...T₄₅₅RDGG₄₅₉.N₄₆₁..R₄₆₉..G₄₇₂GN₄₇₄ in gp120, which correspond to amino acid positions 169, 171-176, 229-232, 235, 319-323, 325, 333, 336-338 in SEQ ID NO: 45. The heavy chain of a VRC01 or VRC03-like antibody can be complemented by the light chain of VRC01, VRC02 and/or VRC03 and still retain binding for gp120, for example retain specific binding for residues 276, 278-283, 365-368, 371, 455-459, 461, 469, and 472-474 of gp120 (see FIGS. 83-91 and 93-97). Thus, in some embodiments, a disclosed antibody includes the heavy chain CDRs from any one of SEQ ID NOs: 1, 3, 27, and 760-1459 and a light chain from any one of SEQ ID NOs: 2, 4, and 28 and wherein the antibody specifically binds to residues 276, 278-283, 365-368, 371, 455-459, 461, 469, and 472-474 of gp120. In some embodiments, a disclosed antibody includes the heavy chain set forth as any one of SEQ ID NOs: 1, 3, 27, and 760-1459 and a light chain set forth as any one of SEQ ID NOs: 2, 4, and 28 and wherein the antibody specifically binds to residues 276, 278-283, 365-368, 371, 455-459, 461, 469 and 472-474 of gp120.

HIV-1 resists neutralization by most antibodies. However, the antibody VRC01, disclosed herein, successfully neutralizes over 90% of current circulating HIV-1 isolates. Another antibody disclosed herein, VRC03, successfully neutralizes over 50% of current circulating HIV-1 isolates. Antibodies VRC01 and VRC03 share only about 50% sequence identity in their variable domains, and there are a number of differences in their activity, including differential induction of antibody 17b binding and CCR5 recognition (VRC01 induces these, whereas VRC03 does not). Nonetheless, crystal structures of VRC01 and VRC03 show virtual identical arrangements of heavy chain and light chain recognition of HIV-1 gp120. The similar recognition by VRC01 and VRC03 antibodies of gp120 indicate that they are members of a class of antibodies, are able to recognize and to neutralize HIV-1 through a similar mode of binding. Thus, these two antibodies, along with the third antibody VRC02 are representative members of a class of antibodies known as VRC01-like antibodies. Thus, disclosed herein are VRC01-like antibodies. While VRC01, VRC02 and VRC03 are representative members of this class of antibodies, using 454 sequencing, 700 additional VRC01 and VRC03-like antibodies have been identified. SEQ ID NOs: 60-759 are nucleic acid sequences encoding the heavy chains of VRC01 and VRC03 like antibodies. SEQ ID NOs: 760-1459 are amino acid sequences the heavy chains of VRC01 and VRC03 like antibodies.

The heavy and light chains of VRC01 and VRC03 can be swapped for partial complementation. For example, the VRC01 light chain and VRC03 heavy chain form active antibodies able to recognize HIV-1. In addition the VRC01 heavy chain and VRC03 light chain form active antibodies that recognize HIV-1. Thus, disclosed herein are VCR01-like antibodies that can be identified by complementation of the heavy or light chains of VCR01 and VCR03. For example, using complementation, the heavy chain amino acid sequences of SEQ ID NOs: 760-1459 are demonstrated to be VRC01 and VRC03-like antibodies that specifically bind gp120. Analysis of these antibodies found a number of sequences, of less than 75% to either VRC01 or VRC03 antibodies, which bioinformatics analysis indicate recognize and neutralize HIV-1. Thus, disclosed herein is a class of antibodies, VRC01-like antibodies, that recognize and neutralize HIV-1. Deep sequencing of heavy chains related to VRC01 in HIV-1 infected individuals with high CD4-binding-site antibody titers reveles sequences, for which bioinformatics analysis enables quick identification of those which can bind and neutralize HIV-1, for example as a way to facilitate antibody discovery. In some embodiments, the VRC01 and VRC03-like antibodies, and other VRC01-like antibodies compete with CD4 for binding to gp120.

As disclosed herein, deep sequencing results define the variation allowed for VRC01-like recognition, and relating this to germ-line VH sequences, which delineated maturation pathways to elicit additional neutralizing antibodies that bind to substantially similar epitopes on the surface of gp120 in substantially the same orientation that VRC01, VRC02 and/or VRC03 bind. Thus a method is disclosed herein to determine if antibodies are in the same class specifically using complementation of antibody H/L for function. For example, if chimeras of one antibody heavy chain with another's light chain (and vice-versa) allows for preservation of binding and neutralization, those two antibodies bind/function in the same mode and thus are members of the same class. Thus, any antibody that preserves antigen binding or HIV neutralization function by chain complementation with VRC01, VRC02 and/or VRC03 is considered a VRC01-like antibody.

The present disclosure also relates to the crystals obtained from the VRC03 or VRC01 antibody or portions thereof in complex with gp120, the crystal structures of the VRC03 or VRC01 antibody or portions thereof in complex with gp120, the three-dimensional coordinates of the VRC03 or VRC01 antibody or portions thereof in complex with gp120 and three-dimensional structures of models of the VRC03 or VRC01 antibody or portions thereof in complex with gp120. The three dimensional coordinates of VRC01 in complex with gp120 are available at the Protein Data Bank, at accession number 3NGB, and are incorporated herein by reference in their entirety as available Jul. 7, 2010. The three dimensional coordinates of VRC03 in complex with gp120 are given in Table 1 of Provisional Application No. 61/402,314, filed Aug. 27, 2010, and are incorporated herein by reference in their entirety.

The crystal structure of the VRC03 or the VRC01 antibody in complex with gp120 provides insight for a novel binding mode for antibodies and gp120. Such a novel binding mode establishes a new class of antibody recognition for gp120 that is indicative of a novel class of gp120 antibodies, as exemplified by VRC01, VRC02 and VRC03. Such antibodies are termed VRC01-like antibodies. In certain embodiments a VRC01-like antibody has a relative angle and orientation of binding of gp120 as shown in the crystal structure of the complex of the VRCR03 antibody and gp120 (see FIG. 2d of Zhou et al., “Structural Basis for Broad and Potent Neutralization of HIV-1 by Antibody VRC01, Science 329, 811-817 (2010), which is incorporated herein by reference in its entirety). In some examples, the VRC01-like antibodies partially mimic the binding of the CD4 receptor, with an about 6 Å shift and an about 43 degree rotation from the CD4-defined position (see FIG. 2d of Zhou et al., “Structural Basis for Broad and Potent Neutralization of HIV-1 by Antibody VRC01, Science 329, 811-817 (2010), which is incorporated herein by reference in its entirety), such as about a 45 degree rotation from the CD4-defined binding, for example about a 40 degree rotation, about a 50 degree rotation, about a 35 degree rotation or about a 55 degree rotation. In some examples, a VRC01-like antibody is an antibody with heavy and light chain in an orientation of heavy chain relative to gp120, that differs by less than 10 about degrees, such as less than about 9 about degrees, less than about 8 about degrees, less than about 7 about degrees, less than about 6 about degrees, less than about 5 about degrees, or less than about 4 degrees and/or less than about a 5 Å translation from the binding angle of VRC01 and/or VRC03 to gp120, such as less than about a 5 Å translation, such as less than about a 4 Å translation, than about a 3 Å translation, less than about a 2 Å translation, or less than about a 2 Å translation. Such a binding characteristic can readily be determined from the crystal structure of the VRC03 or VRC01 antibody complex.

Those of skill in the art will understand that a set of structure coordinates for the VRC01 or VRC03 antibody or portions thereof in complex with gp120 or a portion thereof, is a relative set of points that define a shape in three dimensions. Thus, it is possible that an entirely different set of coordinates could define a similar or identical shape. Moreover, slight variations in the individual coordinates will have little effect on overall shape. The variations in coordinates discussed above may be generated because of mathematical manipulations of the structure coordinates.

This disclosure further provides systems, such as computer systems, intended to generate structures and/or perform rational drug or compound design for an antigenic compound capable of eliciting an immune response in a subject. The system can contain one or more or all of: atomic co-ordinate data according to VRC03 or VRC01 antibody complex or a subset thereof, and the figures derived therefrom by homology modeling, the data defining the three-dimensional structure of a VRC03 or VRC01 antibody complex or at least one sub-domain thereof, or structure factor data for gp120, the structure factor data being derivable from the atomic co-ordinate data of VRC03 or VRC01 antibody complex or a subset thereof and the figures.

In some embodiments the CDR H2 region (the C″ strand in particular) forms hydrogen-bonds to the b-15 loop of gp120. In some embodiments Asp 368 of gp120 forms a salt-bridge with Arg 71 of the heavy chain. All VRC01-like antibodies need to mimic CD4 with similar heavy chain orientations.

In some embodiments, the human monoclonal antibody specifically binds gp41. Thus, antibodies are provided herein wherein the heavy chain of the antibody comprises SEQ ID NO: 5 wherein one or more of amino acids 106, 107, or 109 of SEQ ID NO: 5 are substituted with a tryptophan. In one example, only amino acid 106 of SEQ ID NO: 5 is substituted with a tryptophan. In another example, only amino acid 107 is substituted for a tryptophan. In an additional example, amino acids 106 and 109 are substituted with a tryptophan. In some embodiments, the human monoclonal antibody comprises the heavy chain amino acid sequence set forth as SEQ ID NOs: 6, 7, 8 or 9.

In a further example, the human monoclonal antibody specifically binds gp41, and includes a heavy chain comprising the amino acid sequence set forth as SEQ ID NO: 5 wherein one or more of amino acids 106, 107, or 109 of SEQ ID NO: 5 are substituted with a tryptophan, and includes a light chain that includes the amino acid sequence set forth as SEQ ID NO: 10.

The heavy and the light chain are selected so that the antibody specifically binds either gp120 or gp41. In one example, the antibody specifically binds gp120 and includes the CDRs of the heavy chain amino acid sequence set forth as one of SEQ ID NO: 1, SEQ ID NO: 3 or SEQ ID NO: 27 or any one of SEQ ID NOs: 760-1459 and the CDRs of the light chain amino acid sequence set forth as one of SEQ ID NO: 2, SEQ ID NO: 4 or SEQ ID NO: 28. Thus, the antibody can specifically bind gp120 and includes the heavy chain amino acid sequence set forth as one of SEQ ID NO: 1, SEQ ID NO: 3 or SEQ ID NO: 27 or any one of SEQ ID NOs: 760-1459, and the light chain amino acid sequence set forth as one of SEQ ID NO: 2, SEQ ID NO: 4 or SEQ ID NO: 28.

In another example, the antibody specifically binds gp41. Thus, the antibody can include the CDRs of the heavy chain amino acid sequence set forth as one of SEQ ID NO: 6-9 and the CDRs of the light chain amino acid sequence set forth as one of SEQ ID NO: 10. The antibody can include the heavy chain amino acid sequence set forth as one of SEQ ID NOs: 6-9 and the light chain amino acid sequence set forth as SEQ ID NO: 10.

Fully human monoclonal antibodies include human framework regions. Thus, any of the antibodies that specifically bind gp120 or gp41 herein can include the human framework region and can include the framework regions of the amino acid sequence set forth in one of SEQ ID NOs: 1-10, 27 and 28. However, the framework regions can be from another source. Additional examples of framework sequences that can be used include the amino acid framework sequences of the heavy and light chains disclosed in PCT Publication No. WO 2006/074071 (see, for example, SEQ ID NOs: 1-16), which is herein incorporated by reference.

The monoclonal antibody can be of any isotype. The monoclonal antibody can be, for example, an IgM or an IgG antibody, such as IgG₁ or an IgG₂. The class of an antibody that specifically binds gp120 or gp41 can be switched with another. In one aspect, a nucleic acid molecule encoding V_(L) or V_(H) is isolated using methods well-known in the art, such that it does not include any nucleic acid sequences encoding the constant region of the light or heavy chain, respectively.

In particular examples, the V_(H) amino acid sequence is SEQ ID NOs: 1, 3, 5, 6, 7, 8, 9, 27 or any one of 760-1459. In other examples, the V_(L) amino acid sequence is SEQ ID NOs: 2, 4, 6, 10 or 28. In further examples, the V_(H) nucleic acid sequence is SEQ ID NOs: 29, 31 or 33. In other examples, the V_(L) nucleic acid sequence is SEQ ID NOs: 30, 32 or 34. The nucleic acid molecule encoding V_(L) or V_(H) is then operatively linked to a nucleic acid sequence encoding a C_(L) or C_(H) from a different class of immunoglobulin molecule. This can be achieved using a vector or nucleic acid molecule that comprises a C_(L) or C_(H) chain, as known in the art. For example, an antibody that specifically binds gp120, such as VRC01, VRC02 or VRC03, that was originally IgM may be class switched to an IgG. Similar class switches can also be achieved with an antibody that specifically binds gp41, such as 2F5, or any of its variants described herein. Class switching can be used to convert one IgG subclass to another, such as from IgG₁ to IgG₂.

In some examples, the disclosed and antibodies are oligomers of antibodies, such as dimers trimers, tetramers, pentamers, hexamers, septamers, octomers and so on. hi some examples, the antibodies are pentamers, for example pentamers of VRC01, VRC03, VRC02, or VRC01 and VRC03 like antibodies. Is a specific example the antibody is a pentameric IgM antibody carrying the VRC01 V region (see e.g. FIG. 92).

By definition, the CDRs of the light chain are bounded by the residues at positions 24 and 34 (L-CDR1), 50 and 56 (L-CDR2), 89 and 97 (L-CDR3); the CDRs of the heavy chain are bounded by the residues at positions 31 and 35b (H-CDR1), 50 and 65 (H-CDR2), 95 and 102 (H-CDR3), using the numbering convention delineated by Kabat et al., (1991) Sequences of Proteins of Immunological Interest, 5th Edition, U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, Bethesda, Md. (NIH Publication No. 91-3242, which is specifically incorporated herein by reference in its entirety).

Antibody fragments are encompassed by the present disclosure, such as Fab, F(ab′)₂, and Fv which include a heavy chain and light chain variable region and specifically bind gp120 or gp41. These antibody fragments retain the ability to selectively bind with the antigen. These fragments include:

(1) Fab, the fragment which contains a monovalent antigen-binding fragment of an antibody molecule, can be produced by digestion of whole antibody with the enzyme papain to yield an intact light chain and a portion of one heavy chain;

(2) Fab′, the fragment of an antibody molecule can be obtained by treating whole antibody with pepsin, followed by reduction, to yield an intact light chain and a portion of the heavy chain; two Fab′ fragments are obtained per antibody molecule;

(3) (Fab′)₂, the fragment of the antibody that can be obtained by treating whole antibody with the enzyme pepsin without subsequent reduction; F(ab′)2 is a dimer of two Fab′ fragments held together by two disulfide bonds;

(4) Fv, a genetically engineered fragment containing the variable region of the light chain and the variable region of the heavy chain expressed as two chains; and

(5) Single chain antibody (such as scFv), defined as a genetically engineered molecule containing the variable region of the light chain, the variable region of the heavy chain, linked by a suitable polypeptide linker as a genetically fused single chain molecule.

(6) A dimer of a single chain antibody (scFV₂), defined as a dimer of a scFV. This has also been termed a “miniantibody.”

Methods of making these fragments are known in the art (see for example, Harlow and Lane, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory, New York, 1988). In several examples, the variable region included in the antibody is the variable region of m912.

In a further group of embodiments, the antibodies are Fv antibodies, which are typically about 25 kDa and contain a complete antigen-binding site with three CDRs per each heavy chain and each light chain. To produce these antibodies, the V_(H) and the V_(L) can be expressed from two individual nucleic acid constructs in a host cell. In particular examples, the V_(H) amino acid sequence includes the CDRs from one of SEQ ID NOs: 1, 3, 5, 6, 7, 8, 9 or 27, or any one of 760-1459. In other examples, the V_(L) amino acid sequence includes the CDRs from SEQ ID NOs: 2, 4, 6 or 28. In additional examples, the V_(H) amino acid sequence includes the amino acid sequence set forth as one of SEQ ID NOs: 1, 3, 5, 6, 7, 8, 9 or 27, or any one of 760-1459. In other examples, the V_(L) amino acid sequence includes the amino acid sequence set forth as SEQ ID NOs: 2, 4, 6 or 28. In further examples, the V_(H) nucleic acid sequence is SEQ ID NOs: 29, 31 or 33. In other examples, the V_(L) nucleic acid sequence is SEQ ID NOs: 30, 32 or 34.

If the V_(H) and the V_(L) are expressed non-contiguously, the chains of the Fv antibody are typically held together by noncovalent interactions. However, these chains tend to dissociate upon dilution, so methods have been developed to crosslink the chains through glutaraldehyde, intermolecular disulfides, or a peptide linker. Thus, in one example, the Fv can be a disulfide stabilized Fv (dsFv), wherein the heavy chain variable region and the light chain variable region are chemically linked by disulfide bonds.

In an additional example, the Fv fragments comprise V_(H) and V_(L) chains connected by a peptide linker. These single-chain antigen binding proteins (scFv) are prepared by constructing a structural gene comprising DNA sequences encoding the V_(H) and V_(L) domains connected by an oligonucleotide. The structural gene is inserted into an expression vector, which is subsequently introduced into a host cell such as E. coli. The recombinant host cells synthesize a single polypeptide chain with a linker peptide bridging the two V domains. Methods for producing scFvs are known in the art (see Whitlow et al., Methods: a Companion to Methods in Enzymology, Vol. 2, page 97, 1991; Bird et al., Science 242:423, 1988; U.S. Pat. No. 4,946,778; Pack et al., Bio/Technology 11:1271, 1993; and Sandhu, supra). Dimers of a single chain antibody (scFV₂), are also contemplated.

Antibody fragments can be prepared by proteolytic hydrolysis of the antibody or by expression in E. coli of DNA encoding the fragment. Antibody fragments can be obtained by pepsin or papain digestion of whole antibodies by conventional methods. For example, antibody fragments can be produced by enzymatic cleavage of antibodies with pepsin to provide a 5S fragment denoted F(ab′)2. This fragment can be further cleaved using a thiol reducing agent, and optionally a blocking group for the sulfhydryl groups resulting from cleavage of disulfide linkages, to produce 3.5S Fab′ monovalent fragments. Alternatively, an enzymatic cleavage using pepsin produces two monovalent Fab′ fragments and an Fc fragment directly (see U.S. Pat. No. 4,036,945 and U.S. Pat. No. 4,331,647, and references contained therein; Nisonhoff et al., Arch. Biochem. Biophys. 89:230, 1960; Porter, Biochem. J. 73:119, 1959; Edelman et al., Methods in Enzymology, Vol. 1, page 422, Academic Press, 1967; and Coligan et al. at sections 2.8.1-2.8.10 and 2.10.1-2.10.4).

Other methods of cleaving antibodies, such as separation of heavy chains to form monovalent light-heavy chain fragments, further cleavage of fragments, or other enzymatic, chemical, or genetic techniques may also be used, so long as the fragments bind to the antigen that is recognized by the intact antibody.

One of skill will realize that conservative variants of the antibodies can be produced. Such conservative variants employed in antibody fragments, such as dsFv fragments or in scFv fragments, will retain critical amino acid residues necessary for correct folding and stabilizing between the V_(H) and the V_(L) regions, and will retain the charge characteristics of the residues in order to preserve the low pI and low toxicity of the molecules Amino acid substitutions (such as at most one, at most two, at most three, at most four, or at most five amino acid substitutions) can be made in the V_(H) and the V_(L) regions to increase yield. In particular examples, the V_(H) sequence is SEQ ID NOs: 1, 3, 5, 6, 7, 8, 9, 27 or any one of SEQ ID NOs: 760-1459. In other examples, the V_(L) sequence is SEQ ID NOs: 2, 4, 6 or 28. Conservative amino acid substitution tables providing functionally similar amino acids are well known to one of ordinary skill in the art. The following six groups are examples of amino acids that are considered to be conservative substitutions for one another:

-   -   1) Alanine (A), Serine (S), Threonine (T);     -   2) Aspartic acid (D), Glutamic acid (E);     -   3) Asparagine (N), Glutamine (Q);     -   4) Arginine (R), Lysine (K);     -   5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); and     -   6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W).

The antibodies disclosed herein can be isolated using cloaked antigens, as described in PCT

Publication No. WO 2009/100376. Briefly, antigens are cloaked to target antigenicity of the antigen to a specific epitope that specifically bound by the antibody of interest, such as a neutralizing antibody.

In some embodiments, the isolated antigens used for antibody isolation include a target epitope defined by atomic coordinates of those amino acids of the antigen that contact an antibody of interest that specifically binds the antigen. The gp120 and pg41 antigens have been modified to substitute the surface exposed amino acids located exterior to the target epitope of gp41 or gp120 to focus the antigenicity of the antigen to the target epitope. For example, the method can remove non-target epitopes that might interfere with specific binding of an antibody to the target epitope on gp120 or gp41. In some examples, the amino acid substitutions result in the antigen not being bound by antibodies in a polyclonal serum that specifically bind surface exposed amino acid residues of the wild-type antigen located exterior of the target epitope. In some embodiments, the amino acid substitutions alter antigenicity of the antigen in vivo as compared to the wild-type antigen (unsubstituted antigen) but do not introduce additional glycosylation sites as compared to the wild-type antigen. In some embodiments, that antigen is glycosylated. In some embodiments the cloaked antigen is modified to substitute one or more residues recognized by the antibody of interest to abolish antigen recognition. In some examples, a biotinylation peptide (for example SEQ ID NO: 26) can be fused to the cloaked antigen. Biotinylated cloaked antigen can then be used to stain and thus identify cells, such as PBMC, expressing an antibody of interest.

Additional recombinant human neutralizing antibodies that specifically bind the same epitope of gp120 bound by the antibodies disclosed herein that specifically bind gp120 (for example, the epitope of gp120 specifically bound by Vc2a11 (VRC01) and Vc2a34 (VRC02), or the specific epitope bound by VRC03, see the examples section below), or human neutralizing antibodies that specifically the same epitope of gp41 bound by antibodies that specifically bind gp41 (for example, the epitope bound by L_(100A)W, F_(100B)W, V_(100D)W, and L_(100A)W-V_(100D)W variants of antibody 2F5, see the Examples section below), can be isolated by screening of a recombinant combinatorial antibody library, such as a Fab phage display library (see, for example, U.S. Patent Application Publication No. 2005/0123900). In some cases the phage display libraries are prepared using cDNAs of the variable regions of heavy and light chains prepared from mRNA derived from human lymphocytes. Methodologies for preparing and screening such libraries are known in the art. There are commercially available kits for generating phage display libraries (for example, the Pharmacia Recombinant Phage Antibody System, Catalog No. 27-9400-01; and the Stratagene SurfZAP™ phage display kit, catalog no. 240612). There are also other methods and reagents that can be used in generating and screening antibody display libraries (see, for example, U.S. Pat. No. 5,223,409; PCT Publication No. WO 92/18619; PCT Publication No. WO 91/17271; PCT Publication No. WO 92/20791; PCT Publication No. WO 92/15679; PCT Publication No. WO 93/01288; PCT Publication No. WO 92/01047; PCT Publication No. WO 92/09690; Fuchs et al., Bio/Technology 9:1370-1372, 1991; Hay et al., Hum. Antibod. Hybridomas 3:81-85, 1992; Huse et al., Science 246:1275-1281, 1989; McCafferty et al., Nature 348:552-554, 1990; Griffiths et al., EMBO J. 12:725-734, 1993)

In one embodiment, to isolate additional human antibodies that specifically bind either gp120 or gp41, a neutralizing antibody that specifically binds gp120 or gp41, as described herein, is first used to select human heavy and light chain sequences having similar binding activity toward gp120 or gp41, such as using the epitope imprinting methods disclosed in PCT Publication No. WO 93/06213. The antibody libraries used in this method are scFv libraries prepared and screened, using methods such as those as described in PCT Publication No. WO 92/01047, McCafferty et al., Nature 348:552-554, 1990; and/or Griffiths et al., EMBO J. 12:725-734, 1993 using gp120.

Once initial human variable light chain (V_(L)) and variable heavy chain (V_(H)) segments are selected, “mix and match” experiments, in which different pairs of the initially selected V_(L) and V_(H) segments are screened for gp120 or gp41 binding, such as to the epitopes bound by VRC01, VRC02, and VRC03 (gp120) or to the epitope bound by the L_(100A)W, F_(100B)W, V_(100D)W, and L_(100A)W-V_(100D)W variants of antibody 2F5 (in gp41) are performed to select V_(L)/V_(H) pair combinations of interest. Additionally, to increase binding affinity of the antibody, the V_(L) and V_(H) segments can be randomly mutated, such as within H-CDR3 region or the L-CDR3 region, in a process analogous to the in vivo somatic mutation process responsible for affinity maturation of antibodies during a natural immune response. This in vitro affinity maturation can be accomplished by amplifying V_(H) and V_(L) regions using PCR primers complementary to the H-CDR3 or L-CDR3, respectively. In this process, the primers have been “spiked” with a random mixture of the four nucleotide bases at certain positions such that the resultant PCR products encode V_(H) and V_(L) segments into which random mutations have been introduced into the V_(H) and/or V_(L) CDR3 regions. These randomly mutated V_(H) and V_(L) segments can be tested to determine the binding affinity for gp120 or gp41. In particular examples, the V_(H) amino acid sequence is SEQ ID NOs: 1, 3, 5, 6, 7, 8, 9, 27, or any one of 760-1459. In other examples, the V_(L) amino acid sequence is SEQ ID NOs: 2, 4, 6 or 28.

Following screening and isolation of an antibody that binds gp120 or gp41 from a recombinant immunoglobulin display library, nucleic acid encoding the selected antibody can be recovered from the display package (for example, from the phage genome) and subcloned into other expression vectors by standard recombinant DNA techniques, as described herein. If desired, the nucleic acid can be further manipulated to create other antibody fragments, also as described herein. To express a recombinant antibody isolated by screening of a combinatorial library, the DNA encoding the antibody is cloned into a recombinant expression vector and introduced into a mammalian host cells, as described herein.

The antibodies or antibody fragments disclosed herein can be derivatized or linked to another molecule (such as another peptide or protein). In general, the antibody or portion thereof is derivatized such that the binding to gp120 or gp41 is not affected adversely by the derivatization or labeling. For example, the antibody can be functionally linked (by chemical coupling, genetic fusion, noncovalent association or otherwise) to one or more other molecular entities, such as another antibody (for example, a bispecific antibody or a diabody), a detection agent, a pharmaceutical agent, and/or a protein or peptide that can mediate associate of the antibody or antibody portion with another molecule (such as a streptavidin core region or a polyhistidine tag).

One type of derivatized antibody is produced by cross-linking two or more antibodies (of the same type or of different types, such as to create bispecific antibodies). Suitable crosslinkers include those that are heterobifunctional, having two distinctly reactive groups separated by an appropriate spacer (such as m-maleimidobenzoyl-N-hydroxysuccinimide ester) or homobifunctional (such as disuccinimidyl suberate). Such linkers are available from Pierce Chemical Company (Rockford, Ill.).

An antibody that specifically binds gp120 or gp41 can be labeled with a detectable moiety. Useful detection agents include fluorescent compounds, including fluorescein, fluorescein isothiocyanate, rhodamine, 5-dimethylamine-1-naphthalenesulfonyl chloride, phycoerythrin, lanthanide phosphors and the like. Bioluminescent markers are also of use, such as luciferase, Green fluorescent protein, Yellow fluorescent protein. An antibody can also be labeled with enzymes that are useful for detection, such as horseradish peroxidase, β-galactosidase, luciferase, alkaline phosphatase, glucose oxidase and the like. When an antibody is labeled with a detectable enzyme, it can be detected by adding additional reagents that the enzyme uses to produce a reaction product that can be discerned. For example, when the agent horseradish peroxidase is present the addition of hydrogen peroxide and diaminobenzidine leads to a colored reaction product, which is visually detectable. An antibody may also be labeled with biotin, and detected through indirect measurement of avidin or streptavidin binding. It should be noted that the avidin itself can be labeled with an enzyme or a fluorescent label.

An antibody may be labeled with a magnetic agent, such as gadolinium. Antibodies can also be labeled with lanthanides (such as europium and dysprosium), and manganese. Paramagnetic particles such as superparamagnetic iron oxide are also of use as labels. An antibody may also be labeled with a predetermined polypeptide epitopes recognized by a secondary reporter (such as leucine zipper pair sequences, binding sites for secondary antibodies, metal binding domains, epitope tags). In some embodiments, labels are attached by spacer arms of various lengths to reduce potential steric hindrance.

An antibody can also be labeled with a radiolabeled amino acid. The radiolabel may be used for both diagnostic and therapeutic purposes. Examples of labels for polypeptides include, but are not limited to, the following radioisotopes or radionucleotides: ³H, ¹⁴C, ¹⁵N, ³⁵S, ⁹⁰Y, ⁹⁹Tc, ¹¹¹In, ¹²⁵I, ¹³¹I.

An antibody can also be derivatized with a chemical group such as polyethylene glycol (PEG), a methyl or ethyl group, or a carbohydrate group. These groups may be useful to improve the biological characteristics of the antibody, such as to increase serum half-life or to increase tissue binding.

Means of detecting such labels are well known to those of skill in the art. Thus, for example, radiolabels may be detected using photographic film or scintillation counters, fluorescent markers may be detected using a photodetector to detect emitted illumination. Enzymatic labels are typically detected by providing the enzyme with a substrate and detecting the reaction product produced by the action of the enzyme on the substrate, and colorimetric labels are detected by simply visualizing the colored label.

B. Polynucleotides and Expression

Nucleic acid molecules (also referred to as polynucleotides) encoding the polypeptides provided herein (including, but not limited to antibodies) can readily be produced by one of skill in the art. For example, these nucleic acids can be produced using the amino acid sequences provided herein (such as the CDR sequences, heavy chain and light chain sequences), sequences available in the art (such as framework sequences), and the genetic code. The nucleic acids encoding the VRC01 heavy chain was deposited as ATCC Deposit Number PTA-10412; the nucleic acids encoding the VRC01 light chain was deposited as ATCC Deposit Number PTA-10411; the nucleic acids encoding the VRC02 heavy chain was deposited as ATCC Deposit Number PTA-10414; and the nucleic acid encoding the VRC02 light chain was deposited as ATCC Deposit Number PTA-10413. Nucleic acids encoding the VRC03 heavy chain and VRC03 light chain were deposited at the ATCC on Dec. 23, 2009 as ATCC Deposit Numbers PTA-10551 and PTA-10550, respectively. All deposits were made in accordance with the Budapest Treaty.

V_(H) nucleic acid sequences are set forth as SEQ ID NOs: 29, 31, 33, and any one of 61-759 and include degenerate variants thereof. V_(L) nucleic acid sequences are set forth as SEQ ID NOs: 30, 32 and 34, and include degenerate variants thereof. One of skill in the art can readily use the genetic code to construct a variety of functionally equivalent nucleic acids, such as nucleic acids which differ in sequence but which encode the same antibody sequence, or encode a conjugate or fusion protein including the V_(L) and/or V_(H) nucleic acid sequence.

Nucleic acid sequences encoding the antibodies that specifically bind gp120 or gp41 can be prepared by any suitable method including, for example, cloning of appropriate sequences or by direct chemical synthesis by methods such as the phosphotriester method of Narang et al., Meth. Enzymol. 68:90-99, 1979; the phosphodiester method of Brown et al., Meth. Enzymol. 68:109-151, 1979; the diethylphosphoramidite method of Beaucage et al., Tetra. Lett. 22:1859-1862, 1981; the solid phase phosphoramidite triester method described by Beaucage & Caruthers, Tetra. Letts. 22(20):1859-1862, 1981, for example, using an automated synthesizer as described in, for example, Needham-VanDevanter et al., Nucl. Acids Res. 12:6159-6168, 1984; and, the solid support method of U.S. Pat. No. 4,458,066. Chemical synthesis produces a single stranded oligonucleotide. This can be converted into double stranded DNA by hybridization with a complementary sequence or by polymerization with a DNA polymerase using the single strand as a template. One of skill would recognize that while chemical synthesis of DNA is generally limited to sequences of about 100 bases, longer sequences may be obtained by the ligation of shorter sequences.

Exemplary nucleic acids can be prepared by cloning techniques. Examples of appropriate cloning and sequencing techniques, and instructions sufficient to direct persons of skill through many cloning exercises are found in Sambrook et al., supra, Berger and Kimmel (eds.), supra, and Ausubel, supra. Product information from manufacturers of biological reagents and experimental equipment also provide useful information. Such manufacturers include the SIGMA Chemical Company (Saint Louis, Mo.), R&D Systems (Minneapolis, Minn.), Pharmacia Amersham (Piscataway, N.J.), CLONTECH Laboratories, Inc. (Palo Alto, Calif.), Chem Genes Corp., Aldrich Chemical Company (Milwaukee, Wis.), Glen Research, Inc., GIBCO BRL Life Technologies, Inc. (Gaithersburg, Md.), Fluka Chemica-Biochemika Analytika (Fluka Chemie AG, Buchs, Switzerland), Invitrogen (Carlsbad, Calif.), and Applied Biosystems (Foster City, Calif.), as well as many other commercial sources known to one of skill.

Nucleic acids can also be prepared by amplification methods. Amplification methods include polymerase chain reaction (PCR), the ligase chain reaction (LCR), the transcription-based amplification system (TAS), the self-sustained sequence replication system (3SR). A wide variety of cloning methods, host cells, and in vitro amplification methodologies are well known to persons of skill.

Any of the nucleic acids encoding any of the antibodies, V_(H) and/or V_(L), disclosed herein (or fragment thereof) can be expressed in a recombinantly engineered cell such as bacteria, plant, yeast, insect and mammalian cells. These antibodies can be expressed as individual V_(H) and/or V_(L) chain, or can be expressed as a fusion protein. An immunoadhesin can also be expressed. Thus, in some examples, nucleic acids encoding a V_(H) and V_(L), and immunoadhesin are provided. The nucleic acid sequences can optionally encode a leader sequence.

To create a single chain antibody, (scFv) the V_(H)- and V_(L)-encoding DNA fragments are operatively linked to another fragment encoding a flexible linker, e.g., encoding the amino acid sequence (Gly₄-Ser)₃, such that the V_(H) and V_(L) sequences can be expressed as a contiguous single-chain protein, with the V_(L) and V_(H) domains joined by the flexible linker (see, e.g., Bird et al., Science 242:423-426, 1988; Huston et al., Proc. Natl. Acad. Sci. USA 85:5879-5883, 1988; McCafferty et al., Nature 348:552-554, 1990). Optionally, a cleavage site can be included in a linker, such as a furin cleavage site.

The nucleic acid encoding the V_(H) and/or the V_(L) optionally can encode an Fc domain (immunoadhesin). The Fc domain can be an IgA, IgM or IgG Fc domain. The Fc domain can be an optimized Fc domain, as described in U.S. Published Patent Application No. 20100/093979, incorporated herein by reference. In one example, the immunoadhesin is an IgG₁ Fc.

The single chain antibody may be monovalent, if only a single V_(H) and V_(L) are used, bivalent, if two V_(H) and V_(L) are used, or polyvalent, if more than two V_(H) and V_(L) are used. Bispecific or polyvalent antibodies may be generated that bind specifically to gp120 and to another molecule, such as gp41. The encoded V_(H) and V_(L) optionally can include a furin cleavage site between the V_(H) and V_(L) domains.

It is expected that those of skill in the art are knowledgeable in the numerous expression systems available for expression of proteins including E. coli, other bacterial hosts, yeast, and various higher eukaryotic cells such as the COS, CHO, HeLa and myeloma cell lines.

The host cell can be a gram positive bacteria including, but are not limited to, Bacillus, Streptococcus, Streptomyces, Staphylococcus, Enterococcus, Lactobacillus, Lactococcus, Clostridium, Geobacillus, and Oceanobacillus. Methods for expressing protein in gram positive bacteria, such as Lactobaccillus are well known in the art, see for example, U.S. Published Patent Application No. 20100/080774. Expression vectors for lactobacillus are described, for example in U.S. Pat. No. 6,100,388, and U.S. Pat. No. 5,728,571. Leader sequences can be included for expression in Lactobacillus. Gram negative bacteria include, but not limited to, E. coli, Pseudomonas, Salmonella, Campylobacter, Helicobacter, Flavobacterium, Fusobacterium, Ilyobacter, Neisseria, and Ureaplasma.

One or more DNA sequences encoding the antibody or fragment thereof can be expressed in vitro by DNA transfer into a suitable host cell. The cell may be prokaryotic or eukaryotic. The term also includes any progeny of the subject host cell. It is understood that all progeny may not be identical to the parental cell since there may be mutations that occur during replication. Methods of stable transfer, meaning that the foreign DNA is continuously maintained in the host, are known in the art. Hybridomas expressing the antibodies of interest are also encompassed by this disclosure.

The expression of nucleic acids encoding the isolated proteins described herein can be achieved by operably linking the DNA or cDNA to a promoter (which is either constitutive or inducible), followed by incorporation into an expression cassette. The promoter can be any promoter of interest, including a cytomegalovirus promoter and a human T cell lymphotrophic virus promoter (HTLV)-1. Optionally, an enhancer, such as a cytomegalovirus enhancer, is included in the construct. The cassettes can be suitable for replication and integration in either prokaryotes or eukaryotes. Typical expression cassettes contain specific sequences useful for regulation of the expression of the DNA encoding the protein. For example, the expression cassettes can include appropriate promoters, enhancers, transcription and translation terminators, initiation sequences, a start codon (i.e., ATG) in front of a protein-encoding gene, splicing signal for introns, sequences for the maintenance of the correct reading frame of that gene to permit proper translation of mRNA, and stop codons. The vector can encode a selectable marker, such as a marker encoding drug resistance (for example, ampicillin or tetracycline resistance).

To obtain high level expression of a cloned gene, it is desirable to construct expression cassettes which contain, at the minimum, a strong promoter to direct transcription, a ribosome binding site for translational initiation (internal ribosmal binding sequences), and a transcription/translation terminator. For E. coli, this includes a promoter such as the T7, trp, lac, or lambda promoters, a ribosome binding site, and preferably a transcription termination signal. For eukaryotic cells, the control sequences can include a promoter and/or an enhancer derived from, for example, an immunoglobulin gene, HTLV, SV40 or cytomegalovirus, and a polyadenylation sequence, and can further include splice donor and/or acceptor sequences (for example, CMV and/or HTLV splice acceptor and donor sequences). The cassettes can be transferred into the chosen host cell by well-known methods such as transformation or electroporation for E. coli and calcium phosphate treatment, electroporation or lipofection for mammalian cells. Cells transformed by the cassettes can be selected by resistance to antibiotics conferred by genes contained in the cassettes, such as the amp, gpt, neo and hyg genes.

When the host is a eukaryote, such methods of transfection of DNA as calcium phosphate coprecipitates, conventional mechanical procedures such as microinjection, electroporation, insertion of a plasmid encased in liposomes, or virus vectors may be used. Eukaryotic cells can also be cotransformed with polynucleotide sequences encoding the antibody, labeled antibody, or functional fragment thereof, and a second foreign DNA molecule encoding a selectable phenotype, such as the herpes simplex thymidine kinase gene. Another method is to use a eukaryotic viral vector, such as simian virus 40 (SV40) or bovine papilloma virus, to transiently infect or transform eukaryotic cells and express the protein (see for example, Eukaryotic Viral Vectors, Cold Spring Harbor Laboratory, Gluzman ed., 1982). One of skill in the art can readily use an expression systems such as plasmids and vectors of use in producing proteins in cells including higher eukaryotic cells such as the COS, CHO, HeLa and myeloma cell lines.

Modifications can be made to a nucleic acid encoding a polypeptide described herein without diminishing its biological activity. Some modifications can be made to facilitate the cloning, expression, or incorporation of the targeting molecule into a fusion protein. Such modifications are well known to those of skill in the art and include, for example, termination codons, a methionine added at the amino terminus to provide an initiation, site, additional amino acids placed on either terminus to create conveniently located restriction sites, or additional amino acids (such as poly His) to aid in purification steps. In addition to recombinant methods, the immunoconjugates, effector moieties, and antibodies of the present disclosure can also be constructed in whole or in part using standard peptide synthesis well known in the art.

Once expressed, the recombinant immunoconjugates, antibodies, and/or effector molecules can be purified according to standard procedures of the art, including ammonium sulfate precipitation, affinity columns, column chromatography, and the like (see, generally, R. Scopes, PROTEIN PURIFICATION, Springer-Verlag, N.Y., 1982). The antibodies, immunoconjugates and effector molecules need not be 100% pure. Once purified, partially or to homogeneity as desired, if to be used therapeutically, the polypeptides should be substantially free of endotoxin.

Methods for expression of antibodies and/or refolding to an appropriate active form, including single chain antibodies, from bacteria such as E. coli have been described and are well-known and are applicable to the antibodies disclosed herein. See, Buchner et al., Anal. Biochem. 205:263-270, 1992; Pluckthun, Biotechnology 9:545, 1991; Huse et al., Science 246:1275, 1989 and Ward et al., Nature 341:544, 1989.

Often, functional heterologous proteins from E. coli or other bacteria are isolated from inclusion bodies and require solubilization using strong denaturants, and subsequent refolding. During the solubilization step, as is well known in the art, a reducing agent must be present to separate disulfide bonds. An exemplary buffer with a reducing agent is: 0.1 M Tris pH 8, 6 M guanidine, 2 mM EDTA, 0.3 M DTE (dithioerythritol). Reoxidation of the disulfide bonds can occur in the presence of low molecular weight thiol reagents in reduced and oxidized form, as described in Saxena et al., Biochemistry 9: 5015-5021, 1970, and especially as described by Buchner et al., supra.

Renaturation is typically accomplished by dilution (for example, 100-fold) of the denatured and reduced protein into refolding buffer. An exemplary buffer is 0.1 M Tris, pH 8.0, 0.5 M L-arginine, 8 mM oxidized glutathione (GSSG), and 2 mM EDTA.

As a modification to the two chain antibody purification protocol, the heavy and light chain regions are separately solubilized and reduced and then combined in the refolding solution. An exemplary yield is obtained when these two proteins are mixed in a molar ratio such that a 5-fold molar excess of one protein over the other is not exceeded. Excess oxidized glutathione or other oxidizing low molecular weight compounds can be added to the refolding solution after the redox-shuffling is completed.

In addition to recombinant methods, the antibodies, labeled antibodies and functional fragments thereof that are disclosed herein can also be constructed in whole or in part using standard peptide synthesis. Solid phase synthesis of the polypeptides of less than about 50 amino acids in length can be accomplished by attaching the C-terminal amino acid of the sequence to an insoluble support followed by sequential addition of the remaining amino acids in the sequence. Techniques for solid phase synthesis are described by Barany & Merrifield, The Peptides: Analysis, Synthesis, Biology. Vol. 2: Special Methods in Peptide Synthesis, Part A. pp. 3-284; Merrifield et al., J. Am. Chem. Soc. 85:2149-2156, 1963, and Stewart et al., Solid Phase Peptide Synthesis, 2nd ed., Pierce Chem. Co., Rockford, Ill., 1984. Proteins of greater length may be synthesized by condensation of the amino and carboxyl termini of shorter fragments. Methods of forming peptide bonds by activation of a carboxyl terminal end (such as by the use of the coupling reagent N, N′-dicylohexylcarbodimide) are well known in the art.

C. Isolation of Additional Antibodies with Enhanced Binding Properties

Epitope scaffolds have been used to isolate antibodies with particular binding specificity (See PCT Publication No. WO 2008/025015). Briefly, an epitope, such as an epitope of a pathogenic agent (for example, an epitope of an HIV-1 polypeptide) recognized by broadly neutralizing antibodies is placed into an appropriate peptide scaffold that preserves its structure and antigenicity. Such epitope scaffolds can then be used as an immunogen to elicit an epitope-specific antibody response in a subject. In another example, such scaffolds can be used to identify specific serum reactivities against the target epitope of the scaffold. This scaffolding technology is applicable not only to HIV-1, but to any pathogen for which a broadly neutralizing antibody and its respective epitope has been characterized at the atomic-level.

The design of epitope-protein scaffolds which elicit selected neutralizing antibodies is disclosed in PCT Publication No. WO 2008/025015, which is incorporated herein by reference. In general, the protocols utilize searchable databases containing the three dimensional structure of proteins, epitopes, and epitope-antibody complexes to identify proteins that are capable of structurally accommodating at least one selected epitope on their surface. Protein folding energetic predictions are further utilized to make energetic predictions. The predicted energies may be used to optimize the structure of the epitope-scaffold and filter results on the basis of energy criteria in order to reduce the number of candidate proteins and identify energetically stable epitope-scaffolds.

In one embodiment, a “superposition” epitope-scaffold can be designed and utilized. Superposition epitope-scaffolds are based upon scaffold proteins having an exposed segment on their surface with a similar conformation as a selected target epitope. The backbone atoms in this superposition region can be structurally superimposed onto the target epitope with less than a selected level of deviation from their native configuration. Candidate scaffolds are identified by computationally searching through a library of three-dimensional structures. The candidate scaffolds are further designed by putting epitope residues in the superposition region of the scaffold protein and making additional mutations on the surrounding surface of the scaffold to prevent undesirable interactions between the scaffold and the epitope or the scaffold and the antibody.

Superposition is advantageous in that it is a conservative technique. Epitope-scaffolds designed by superposition require only a limited number of mutations on the surface of known, stable proteins. Thus, the designs can be produced rapidly and a high fraction of the first round designs are likely to fold properly.

In another embodiment, “grafting” epitope scaffolds are utilized. Grafting epitope scaffolds utilize scaffold proteins that can accommodate replacement of an exposed segment with the crystallized conformation of the target epitope. For each suitable scaffold identified by computationally searching through a database of known three-dimensional structures, an exposed segment is replaced by the target epitope. The surrounding protein side chains are further mutated to accommodate and stabilize the inserted epitope. Mutations are further made on the surface of the scaffold to avoid undesirable interactions between the scaffold and epitope or scaffold and antibody. Grafting epitope-scaffolds should substantially mimic the epitope-antibody interaction, as the epitope is presented in substantially its native conformation. As such, grafting may be utilized to treat complex epitopes which are more difficult to incorporate using superposition techniques.

In certain embodiments, protein and design calculations are performed using the ROSETTA™ computer program to design the eptiope scaffolds. ROSETTA™ is a software application, developed at least in part at the University of Washington which provides protein structure predictions. ROSETTA™ utilizes physical models of the macromolecular interactions and algorithms for finding the lowest energy structure for an amino acid sequence in order to predict the structure of a protein. Furthermore ROSETTA™ may use these models and algorithms to find the lowest energy amino acid sequence for a protein or protein-protein complex for protein design. The ROSETTA™ energy function and several modules of the ROSETTA™ protein structure modeling and design platform are employed in the protein scaffold design discussed below.

Described herein are methods of increasing an antibody binding affinity and neutralizing capacity that utilize this epitope scaffolding technology. In the methods described herein, an original (parental) antibody that specifically binds a scaffolded epitope is identified and sequenced. The antibody binding determinants of antibody reactivity are then identified by mutagenesis (for example, amino acid substitutions) of the antibody sequences, wherein variant antibodies are produced. These amino acid substitutions can be made in one or more CDRs and/or in one or more framework regions of the original antibody. The amino acid substitutions can be a replacement of the amino acid in the original antibody for a tryptophan. In some embodiments, the antibodies include at most one, at most two, at most three or at most four amino acids substitutions, such as in the CDRs. These variant antibodies, such as the antibodies including one, two, three or four amino acids substitutions, are then evaluated for binding to the epitope scaffold. Antibodies are selected that have altered binding affinity for the epitope scaffold as compared to the original (parental) antibody.

In particular examples, selection of residues for mutagenesis is aided by structural modeling of the scaffold-antibody interaction. To produce an antibody with enhanced binding affinity, the amino acid(s) that have been identified as critical for antibody reactivity are then further substituted and the effects on antibody reactivity measured by further probing with the epitope scaffold.

Any method known to the art can be used to determine antibody-scaffold affinity. In some examples, the epitope scaffold probe is fused to a biotinylation peptide. In particular examples, the biotinylation peptide is SEQ ID NO: 26.

In some examples, the amino acid residues in the antibody that are responsible for specific binding to the epitope are indicated by a decrease in antibody affinity of the variant antibody as compared to the parental antibody. hi some embodiments, antibodies are selected wherein binding is decreased by at least 20%, at least 30% at least 40% at least 50% at least 100% (2-fold), at least 200%, at least 300%, at least 400%, at least 500%, at least 600%, at least 700%, at least 800%, at least 900%, or at least 1,000% (10-fold) as compared to the original antibody. The decrease of affinity for the scaffold identifies the variant antibody as compared to the parental antibody to identify the one or more amino acids as critical for antigen binding. In one example, the complete loss of antibody binding affinity for the epitope scaffold identifies the one or more amino acid residues as critical for specific binding of antibody to the epitope.

In other embodiments, variant antibodies are selected wherein binding is increased by at least 20%, at least 30% at least 40% at least 50% at least 100% (2-fold), at least 200%, at least 300%, at least 400%, at least 500%, at least 600%, at least 700%, at least 800%, at least 900%, or at least 1,000% (10-fold) as compared to the parental antibody. An increase of the binding of the variant antibody as compared to the parental antibody identifies the one or more amino acid residues as critical for specific binding of the antibody to the epitope.

An exemplary method is disclosed herein (see the EXAMPLES section), wherein this technology is utilized for an antibody that specifically binds an antigenic glycoprotein of HIV. However, this method is broadly applicable to antibodies that specifically bind any antigen of interest. In some embodiments, the antibody specifically binds a pathogen of interest. Pathogens include viruses, fungi, bacteria, and protozoa. In other example the antibody specifically binds a tumor antigen of anteerest.

While this disclosure is written with specific reference to the identification of antibodies that are specific for HIV, such as antibodies specific for gp120 and gp140 from HIV, the methods disclosed herein, including those described in the EXAMPLES are equally applicable to the identification of other antigens, for example antigens from pathogenic sources as well as tumor antigens. In some examples, using the epitope scaffolds such as described in PCT Publication No. WO 2008/025015 can be used to identify epitope specific B-cells and isolate specific IgG clones that bind to a target epitope, such as the site of vulnerability ion the surface of gp120, as disclosed herein. With reference to FIG. 117, in some examples, a subject is selected that produces, or has broadly neutralizing sera, such that the B-cells isolated from that subject are believed express one or more broadly neutralizing antibodies to an antigen of interest, such as an antigen from a pathogenic organism or a tumor (see FIG. 117, 1). B-cells are isolated from the subject, for example using the procedures outlined in the EXAMPLES section, and the isolated B-cells are contacted with a target antigen of interest (see FIG. 117, 2), such as a resurfaced antigen, and the complex of the B-cells and the target antigen of interest is isolated (see FIG. 117, 3). Nucleic acids are obtained from the B-cells are analyzed and antibodies encoded by the Ig gene are synthesized (see FIG. 117, 4) and the antibodies are further characterized (see FIG. 117, 5). In some examples, the antibody antigen complexes are further characterized structurally, for example using X-ray diffraction methods (see FIG. 117, 6), which allows the important antibody/antigen contacts to be mapped. This information can be used to define classes of neutralizing antibodies specific for an antigen of interest, for example as is disclosed herein for the class of VRC01 and VRC03-like antibodies. The structural information about the antigen/antibody contacts and conformation can be analyzed in conjunction with sequencing data, such as 454 sequencing data, to identify additional antibodies that have the same or similar binding properties, in that they are highly specific for a specific neutralizing epitope on the surface of the antigen of interest. By combining sequence analysis, such as 454 sequencing with structural characterization of antibody/antigen interactions at the atomic level it is now possible to identify classes of neutralizing antibodies from a subject. As disclosed herein, this has now been demonstrated for HIV using designed gp120 antigens. In other words, the combination of sequencing, such as 454 sequencing with identified binding motifs in antibodies allows the identification of additional antibodies. Importantly, however, it allows for a short-cut (see e.g. steps 1-7 in FIG. 117) as these antibodies are directly identified from B-cells as these antibodies are directly identified from B-cells without the requirement for isolating antigen specific B cells. In doing so, it ties genomics technologies directly to sera characterization. This tie permits direct interrogation of the antibodyome, which is the family of antibodies specific for an antigen or even an organism or cancer, or interest. In some examples, the methods described herein can be used to examine a time course of antibody maturation from seroconversion to production of broadly neutralizing antibodies. In some embodiments, the methods described herein are used to monitor the development of antibodies in vaccines is a subject, for example to allow feedback at the antibody sequence level and subsequent redesign of the vaccines during vaccine development.

The methods disclosed herein have broad applications for of identifying specific antibodies, classes or species of antibodies with defined specificity, for example as exemplified by the identification of VRC01 and VRC03-like antibodies disclosed herein. This combination of structural and genomic analysis of Ig may provide a generic way of identifying specific antibodies, as well as classes or species of antibodies with defined specificities. Such antibodies, like VRC01 and related antibodies, can potentially be used for prevention strategies, such as microbicides or passive protection of HIV infection, vaccine design, diagnostics, and therapy of infected individuals.

Thus, viral antigenic epitopes can be used with the methods disclosed herein to identify classes of antibodies specific for the antigen of interest. Antigens of use in the methods disclosed herein include, but are not limited to, antigenic epitopes from dengue virus, human immunodeficiency virus, influenza virus, metapneumovirus, norovirus, papillomavirus, parvovirus, SARS virus, smallpox virus, picornaviruses, respiratory syncitial virus, parainfluenza virus, measles, hepatitis, measles, varicella zoster, rabies and West Nile virus, among many others. In some embodiments, the antigenic epitope is from a virus causes a respiratory disorder (for example, adeno, echo, rhino, coxsackie, influenza, parainfluenza, or respiratory syncytial virus), a digestive disorder (for example, rota, parvo, dane particle, or hepatitis A virus), an epidermal-epithelial disorder (for example, verruca, papilloma, molluscum, rubeola, rubella, small pox, cowpox), a herpes virus disease (for example, varicella-zoster, simplex I, or simplex II virus), an arbovirus disease (for example, dengue, yellow, or hemorrhagic fevers), a viral disease of the central nervous system (for example, polio or rabies), a viral heart disease, or acquired immune deficiency (AIDS). The antigenic epitope can also be from a bacteria. In some examples, bacteria antigenic epitope is a Pyogenic cocci antigen from an organism that causes, for example, staphylococcal, streptococcal, pneumococcal, meningococcal, and gonococcal infections; a gram-negative rod antigen from an organism that causes, for example, E. coli, Klebsiella, enterobacter, pseudomonas, or legionella infections; an antigenic epitope for an organism that causes, for example, hemophilus influenza, bordetella pertussis, or diphtheria infections. Also encompassed in this disclosure are bacterial antigens from enteropathic bacteria (for example, S. typhi), clostridia (for example, C. tetani or C. botulinum)), and mycobacteria (for example, M. tuberculosis or M. leprae). Exemplary antigens are the CFP10 polypeptide or a domain of other polypeptides of Mycobacterium tuberculosis, or of a domain of the pilus polypeptide of Vibrio cholera, the CjaA polypeptide of Campylobacter coli, the Sfb1 polypeptide of Streptococcus pyogenes, the UreB polypeptide Helicobacter pylori, or of other pathogenic organisms such as the circumsporozoite polypeptide of Plasmodium falciparum. Non-limiting examples of bacterial (including mycobacterial) epitopes can be found, for example, in Mei et al., Mol. Microbiol. 26:399-407, 1997; and U.S. Pat. No. 6,790,950 (gram negative bacteria); U.S. Pat. No. 6,790,448 (gram positive bacteria); U.S. Pat. Nos. 6,776,993 and 6,384,018 (Mycobacterium tuberculosis).

In additional examples, the antigenic epitope is from a Chlamydia that causes ornithosis (C. psittaci), chlamydial urethritis and cervicitis (C. trachomatis), inclusion conjunctivitis (C. trachomatis), trachoma (C. trachomatis), or lymphogranuloma venereum (C. trachomatis)). In additional examples, the antigen epitope is from rickettsia that causes typhus fever (R. prowazekii), Rocky Mountain spotted fever (R. rickettsi), scrub fever (R. tsutsugamushi) or Q fever (Coxiella burnetti).

In particular embodiments, the antigenic epitope is from a fungus, such as Candidae (for example, C. albicans) or Aspergillis (for example, A. fumigatus). In other embodiments, the protozoan antigen is from, for example, Giardia Lamblia, Trichomoniasis, Pneumocystosis, Plasmodium, Leishmania, or Toxoplasma. In further embodiments, the helminth antigen is from, for example, Trichuris, Necator americanus (hookworm disease), Ancylostoma duodenale (hookworm disease), Trichinella spiralis, or S. mansoni.

In additional embodiments, the method is applied to identify antibodies that bind antigenic epitopes of tumor antigens. Tumor antigens include, but are not limited to carcinoembryonic antigen (“CEA:” e.g., GENBANK® Accession No. AAA62835), ras proteins (see, e.g., Parada et al. Nature 297:474-478, 1982), p53 protein (e.g., GENBANK® Accession No. P07193), prostate-specific antigen (“PSA:” e.g., GENBANK® Accession Nos. NP001639, NP665863), Muc1 (e.g., GENBANK® Accession No. P15941), tyrosinase (see, e.g., Kwon et al., Proc Natl Acad Sci USA 84:7473-7477, 1987, erratum Proc Natl Acad Sci USA 85:6352, 1988 Melanoma-associated antigen (MAGEs: for examples, see, U.S. Pat. Nos. 5,462,871; 5,554,724; 5,554,506; 5,541,104 and 5,558,995). The tumor antigen can be from a tumor of any organ or tissue, including but not limited to solid organ tumors. For example, the tumor can be melanoma, colon-, breast-, lung, cervical-, ovarian, endometrial-, prostate-, skin-, brain-, liver-, kidney, thyroid, pancreatic, esophageal-, or gastric cancer, leukemias, lymphomas, multiple myeloma, myelodysplastic syndrome, premalignant human papilloma virus (HPV)-related lesions, intestinal polyps and other chronic states associated with increased tumor risk.

D. Compositions and Therapeutic Methods

Methods are disclosed herein for the prevention or treatment of an HIV infection, such as an HIV-1 infection. Prevention can include inhibition of infection with HIV-1. The methods include contacting a cell with an effective amount of the human monoclonal antibodies disclosed herein that specifically binds gp120 or gp41, or a functional fragment thereof. The method can also include administering to a subject a therapeutically effective amount of the human monoclonal antibodies to a subject.

Methods to assay for neutralization activity include, but are not limited to, a single-cycle infection assay as described in Martin et al. (2003) Nature Biotechnology 21:71-76. In this assay, the level of viral activity is measured via a selectable marker whose activity is reflective of the amount of viable virus in the sample, and the IC50 is determined. In other assays, acute infection can be monitored in the PM1 cell line or in primary cells (normal PBMC). In this assay, the level of viral activity can be monitored by determining the p24 concentrations using ELISA. See, for example, Martin et al. (2003) Nature Biotechnology 21:71-76.

HIV infection does not need to be completely eliminated for the composition to be effective. For example, a composition can decrease HIV infection by a desired amount, for example by at least 10%, at least 20%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 98%, or even at least 100% (elimination of detectable HIV infected cells), as compared to HIV infection in the absence of the composition. In example, the cell is also contacted with an effective amount of an additional agent, such as anti-viral agent. The cell can be in vivo or in vitro. The methods can include administration of one on more additional agents known in the art. In additional examples, HIV replication can be reduced or inhibited by similar methods. HIV replication does not need to be completely eliminated for the composition to be effective. For example, a composition can decrease HIV replication by a desired amount, for example by at least 10%, at least 20%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 98%, or even at least 100% (elimination of detectable HIV), as compared to HIV replication in the absence of the composition. In one example, the cell is also contacted with an effective amount of an additional agent, such as anti-viral agent. The cell can be in vivo or in vitro.

Compositions are provided that include one or more of the antibodies that specifically bind gp120 or gp41, or functional fragments thereof, that are disclosed herein in a carrier. The compositions can be prepared in unit dosage forms for administration to a subject. The amount and timing of administration are at the discretion of the treating physician to achieve the desired purposes. The antibody can be formulated for systemic or local administration. In one example, the antibody that specifically binds gp120 or gp41 is formulated for parenteral administration, such as intravenous administration.

The compositions for administration can include a solution of the antibody that specifically binds gp120 or the antibody that specifically binds gp41 dissolved in a pharmaceutically acceptable carrier, such as an aqueous carrier. A variety of aqueous carriers can be used, for example, buffered saline and the like. These solutions are sterile and generally free of undesirable matter. These compositions may be sterilized by conventional, well known sterilization techniques. The compositions may contain pharmaceutically acceptable auxiliary substances as required to approximate physiological conditions such as pH adjusting and buffering agents, toxicity adjusting agents and the like, for example, sodium acetate, sodium chloride, potassium chloride, calcium chloride, sodium lactate and the like. The concentration of antibody in these formulations can vary widely, and will be selected primarily based on fluid volumes, viscosities, body weight and the like in accordance with the particular mode of administration selected and the subject's needs.

A typical pharmaceutical composition for intravenous administration includes about 0.1 to 10 mg of antibody per subject per day. Dosages from 0.1 up to about 100 mg per subject per day may be used, particularly if the agent is administered to a secluded site and not into the circulatory or lymph system, such as into a body cavity or into a lumen of an organ. Actual methods for preparing administrable compositions will be known or apparent to those skilled in the art and are described in more detail in such publications as Remington's Pharmaceutical Science, 19th ed., Mack Publishing Company, Easton, Pa. (1995).

Antibodies may be provided in lyophilized form and rehydrated with sterile water before administration, although they are also provided in sterile solutions of known concentration. The antibody solution is then added to an infusion bag containing 0.9% sodium chloride, USP, and typically administered at a dosage of from 0.5 to 15 mg/kg of body weight. Considerable experience is available in the art in the administration of antibody drugs, which have been marketed in the U.S. since the approval of RITUXAN® in 1997. Antibodies can be administered by slow infusion, rather than in an intravenous push or bolus. In one example, a higher loading dose is administered, with subsequent, maintenance doses being administered at a lower level. For example, an initial loading dose of 4 mg/kg may be infused over a period of some 90 minutes, followed by weekly maintenance doses for 4-8 weeks of 2 mg/kg infused over a 30 minute period if the previous dose was well tolerated.

A therapeutically effective amount of a human gp120-specific antibody or human gp41-specific antibody will depend upon the severity of the disease and/or infection and the general state of the patient's health. A therapeutically effective amount of the antibody is that which provides either subjective relief of a symptom(s) or an objectively identifiable improvement as noted by the clinician or other qualified observer. These compositions can be administered in conjunction with another therapeutic agent, either simultaneously or sequentially.

In one embodiment, administration of the antibody results in a reduction in the establishment of HIV infection and/or reducing subsequent HIV disease progression in a subject. A reduction in the establishment of HIV infection and/or a reduction in subsequent HIV disease progression encompass any statistically significant reduction in HIV activity. In some embodiments, methods are disclosed for treating a subject with an HIV-1 infection. These methods include administering to the subject a therapeutically effective amount of an antibody, or a nucleic acid encoding the antibody, thereby preventing or treating the HIV-1 infection.

Studies have shown that the rate of HIV transmission from mother to infant is reduced significantly when zidovudine is administered to HIV-infected women during pregnancy and delivery and to the offspring after birth (Connor et al., 1994 Pediatr Infect Dis J 14: 536-541). Several studies of mother-to-infant transmission of HIV have demonstrated a correlation between the maternal virus load at delivery and risk of HIV transmission to the child. The present disclosure provides isolated human monoclonal antibodies that are of use in decreasing HIV-transmission from mother to infant. Thus, in some examples a therapeutically effective amount of a human gp120-specific antibody or human gp41-specific antibody is administered in order to prevent transmission of HIV, or decrease the risk of transmission of HIV, from a mother to an infant. In some examples, a therapeutically effective amount of the antibody is administered to mother and/or to the child at childbirth. In other examples, a therapeutically effective amount of the antibody is administered to the mother and/or infant prior to breast feeding in order to prevent viral transmission to the infant or decrease the risk of viral transmission to the infant. In some embodiments, both a therapeutically effective amount of the antibody and a therapeutically effective amount of another agent, such as zidovudine, is administered to the mother and/or infant.

For any application, the antibody can be combined with anti-retroviral therapy. Antiretroviral drugs are broadly classified by the phase of the retrovirus life-cycle that the drug inhibits. The disclosed antibodies can be administered in conjunction with Nucleoside and nucleotide reverse transcriptase inhibitors (nRTI), Non-nucleoside reverse transcriptase inhibitors (NNRTI), Protease inhibitors, Entry inhibitors (or fusion inhibitors), Maturation inhibitors, or a Broad spectrum inhibitors, such as natural antivirals. Exemplary agents include lopinavir, ritonavir, zidovudine, lamivudine, tenofovir, emtricitabine and efavirenz.

Single or multiple administrations of the compositions including the antibodies disclosed herein are administered depending on the dosage and frequency as required and tolerated by the patient. In any event, the composition should provide a sufficient quantity of at least one of the antibodies disclosed herein to effectively treat the patient. The dosage can be administered once but may be applied periodically until either a therapeutic result is achieved or until side effects warrant discontinuation of therapy. In one example, a dose of the antibody is infused for thirty minutes every other day. In this example, about one to about ten doses can be administered, such as three or six doses can be administered every other day. In a further example, a continuous infusion is administered for about five to about ten days. The subject can be treated at regular intervals, such as monthly, until a desired therapeutic result is achieved. Generally, the dose is sufficient to treat or ameliorate symptoms or signs of disease without producing unacceptable toxicity to the patient.

Controlled-release parenteral formulations can be made as implants, oily injections, or as particulate systems. For a broad overview of protein delivery systems see, Banga, A. J., Therapeutic Peptides and Proteins: Formulation, Processing, and Delivery Systems, Technomic Publishing Company, Inc., Lancaster, Pa., (1995). Particulate systems include microspheres, microparticles, microcapsules, nanocapsules, nanospheres, and nanoparticles. Microcapsules contain the therapeutic protein, such as a cytotoxin or a drug, as a central core. In microspheres the therapeutic is dispersed throughout the particle. Particles, microspheres, and microcapsules smaller than about 1 μm are generally referred to as nanoparticles, nanospheres, and nanocapsules, respectively. Capillaries have a diameter of approximately 5 μm so that only nanoparticles are administered intravenously. Microparticles are typically around 100 μm in diameter and are administered subcutaneously or intramuscularly. See, for example, Kreuter, J., Colloidal Drug Delivery Systems, J. Kreuter, ed., Marcel Dekker, Inc., New York, N.Y., pp. 219-342 (1994); and Tice & Tabibi, Treatise on Controlled Drug Delivery, A. Kydonieus, ed., Marcel Dekker, Inc. New York, N.Y., pp. 315-339, (1992).

Polymers can be used for ion-controlled release of the antibody compositions disclosed herein. Various degradable and nondegradable polymeric matrices for use in controlled drug delivery are known in the art (Langer, Accounts Chem. Res. 26:537-542, 1993). For example, the block copolymer, polaxamer 407, exists as a viscous yet mobile liquid at low temperatures but forms a semisolid gel at body temperature. It has been shown to be an effective vehicle for formulation and sustained delivery of recombinant interleukin-2 and urease (Johnston et al., Pharm. Res. 9:425-434, 1992; and Pec et al., J. Parent. Sci. Tech. 44(2):58-65, 1990). Alternatively, hydroxyapatite has been used as a microcarrier for controlled release of proteins (Ijntema et al., Int. J. Pharm. 112:215-224, 1994). In yet another aspect, liposomes are used for controlled release as well as drug targeting of the lipid-capsulated drug (Betageri et al., Liposome Drug Delivery Systems, Technomic Publishing Co., Inc., Lancaster, Pa. (1993)). Numerous additional systems for controlled delivery of therapeutic proteins are known (see U.S. Pat. No. 5,055,303; U.S. Pat. No. 5,188,837; U.S. Pat. No. 4,235,871; U.S. Pat. No. 4,501,728; U.S. Pat. No. 4,837,028; U.S. Pat. No. 4,957,735; U.S. Pat. No. 5,019,369; U.S. Pat. No. 5,055,303; U.S. Pat. No. 5,514,670; U.S. Pat. No. 5,413,797; U.S. Pat. No. 5,268,164; U.S. Pat. No. 5,004,697; U.S. Pat. No. 4,902,505; U.S. Pat. No. 5,506,206; U.S. Pat. No. 5,271,961; U.S. Pat. No. 5,254,342 and U.S. Pat. No. 5,534,496).

E. Diagnostic Methods and Kits

A method is provided herein for the detection of the expression of gp120 or gp41 in vitro or in vivo. In one example, expression of gp120 or gp41 is detected in a biological sample, and can be used to detect HIV-1 infection. The sample can be any sample, including, but not limited to, tissue from biopsies, autopsies and pathology specimens. Biological samples also include sections of tissues, for example, frozen sections taken for histological purposes. Biological samples further include body fluids, such as blood, serum, plasma, sputum, spinal fluid or urine.

In several embodiments, a method is provided for detecting AIDS and/or an HIV-1 infection in a subject. The disclosure provides a method for detecting HIV-1 in a biological sample, wherein the method includes contacting a biological sample with the antibody under conditions conducive to the formation of an immune complex, and detecting the immune complex, to detect the gp120 or gp41 in the biological sample. In one example, the detection of gp120 or gp41 in the sample indicates that the subject has an HIV infection. In another example, the detection of gp120 or gp41 in the sample indicates that the subject has AIDS. In another example, detection of gp120 or gp41 in the sample confirms a diagnosis of AIDS and/or an HIV-1 infection in a subject.

In some embodiments, the disclosed antibodies are used to test vaccines. For example to test if a vaccine composition assumes the same conformation as a gp120 or gp41 peptide. Thus provided herein is a method for detecting testing a vaccine, wherein the method includes contacting a sample containing the vaccine, such as a gp120 or gp41 immunogen, with the antibody under conditions conducive to the formation of an immune complex, and detecting the immune complex, to detect the vaccine g in the sample. In one example, the detection of the immune complex in the sample indicates that vaccine component, such as such as a gp120 or gp41 immunogen assumes a conformation capable of binding the antibody.

In one embodiment, the antibody is directly labeled with a detectable label. In another embodiment, the antibody that binds gp120 or gp41 (the first antibody) is unlabeled and a second antibody or other molecule that can bind the antibody that binds gp120 or gp41 is utilized. As is well known to one of skill in the art, a second antibody is chosen that is able to specifically bind the specific species and class of the first antibody. For example, if the first antibody is a human IgG, then the secondary antibody may be an anti-human-IgG. Other molecules that can bind to antibodies include, without limitation, Protein A and Protein G, both of which are available commercially.

Suitable labels for the antibody or secondary antibody are described above, and include various enzymes, prosthetic groups, fluorescent materials, luminescent materials, magnetic agents and radioactive materials. Non-limiting examples of suitable enzymes include horseradish peroxidase, alkaline phosphatase, beta-galactosidase, or acetylcholinesterase. Non-limiting examples of suitable prosthetic group complexes include streptavidin/biotin and avidin/biotin. Non-limiting examples of suitable fluorescent materials include umbelliferone, fluorescein, fluorescein isothiocyanate, rhodamine, dichlorotriazinylamine fluorescein, dansyl chloride or phycoerythrin. A non-limiting exemplary luminescent material is luminol; a non-limiting exemplary a magnetic agent is gadolinium, and non-limiting exemplary radioactive labels include ¹²⁵I, ¹³¹I, ³⁵S or ³H.

The immunoassays and method disclosed herein can be used for a number of purposes. Kits for detecting a polypeptide will typically comprise an antibody that binds gp120 or gp41, such as any of the antibodies disclosed herein. In some embodiments, an antibody fragment, such as an Fv fragment or a Fab is included in the kit. In a further embodiment, the antibody is labeled (for example, with a fluorescent, radioactive, or an enzymatic label).

In one embodiment, a kit includes instructional materials disclosing means of use. The instructional materials may be written, in an electronic form (such as a computer diskette or compact disk) or may be visual (such as video files). The kits may also include additional components to facilitate the particular application for which the kit is designed. Thus, for example, the kit may additionally contain means of detecting a label (such as enzyme substrates for enzymatic labels, filter sets to detect fluorescent labels, appropriate secondary labels such as a secondary antibody, or the like). The kits may additionally include buffers and other reagents routinely used for the practice of a particular method. Such kits and appropriate contents are well known to those of skill in the art.

In one embodiment, the diagnostic kit comprises an immunoassay. Although the details of the immunoassays may vary with the particular format employed, the method of detecting gp120 or gp41 in a biological sample generally includes the steps of contacting the biological sample with an antibody which specifically reacts, under immunologically reactive conditions, to gp120 or gp41. The antibody is allowed to specifically bind under immunologically reactive conditions to form an immune complex, and the presence of the immune complex (bound antibody) is detected directly or indirectly.

F. Deposits

Plasmids including the nucleic acids encoding VRC01 heavy chain, VRC01 light chain, VRC02 heavy chain, VRC02 light chain were deposited in accordance with the Budapest Treaty at the American Type Culture Collection (ATCC) on Oct. 14, 2009. VRC01 heavy chain was deposited as ATCC Deposit Number PTA-10412, VRC01 light chain was deposited as ATCC Deposit Number PTA-10411, VRC02 heavy chain was deposited as ATCC Deposit Number PTA-10414, and VRC02 light chain was deposited as ATCC Deposit Number PTA-10413. Plasmids including nucleic acid sequences encoding the VRC03 heavy chain and VRC03 light chain were deposited in accordance with the Budapest Treaty at the ATCC on Dec. 23, 2009. VRC03 heavy chain was deposited as ATCC Deposit Number PTA-10551, VRC03 light chain was deposited as ATCC Deposit Number PTA-10550.

The following examples are provided to illustrate certain particular features and/or embodiments. These examples should not be construed to limit the disclosure to the particular features or embodiments described.

EXAMPLES Example 1 Identification of Human Monoclonal HIV-1 gp120 Specific Neutralizing Antibodies

This example describes the isolation and characterization of the human monoclonal antibodies VRC01, VRC02, and VRC03.

As disclosed herein, using knowledge of Env structure together with computer-assisted protein recombinant forms of HIV-1 Env were designed that specifically interact with neutralizing antibodies (Nabs) directed to the CD4 binding site (CD4bs) of the HIV gp120 glycoprotein. These Env probes were used to identify and sort individual B cells expressing CD4bs antibodies, enabling the selective isolation of CD4bs-directed monoclonal antibodies (mAbs) with extensive neutralization breadth. To generate a molecule that preserved the antigenic structure of the neutralizing surface of the CD4bs but eliminated other antigenic regions of HIV-1, proteins were designed whose exposed surface residues were substituted with simian immunodeficiency virus (SIV) homologs and other non-HIV-1 residues (FIG. 1A and FIG. 5). These changes were conferred on a core gp120 and a stabilized core gp120, both of which retained the major contact surface for CD4 located on its outer domain. The gp120 core lacked variable regions 1 to 3 and part of the amino and carboxy termini of the full gp120 molecule, and the stabilized core contained crosslinks between different subregions of the core protein. Eight resurfaced proteins were designed and expressed, together with CD4bs mutants that served as negative controls by eliminating binding to the neutralizing mAb b12. Three resurfaced core Envs retained strong reactivity with b12 and mAb 2G12 (FIG. 6), the latter of which recognizes a surface glycan epitope and served as a positive control for a conformationally intact protein. The resurfaced stabilized core 3 (RSC3) was chosen as the preferred candidate for further studies, because a greater percentage of its surface other than the outer domain CD4bs area was altered compared with the other variants (FIG. 6). The conformational integrity and specificity of the RSC3 protein was confirmed by using a panel of known mAbs (FIG. 14, Table S1). As expected, RSC3 displayed strong reactivity to mAb b12 and little or no reactivity to a CD4 fusion protein (FIGS. 1B and 1C). RSC3 also reacted with two weakly neutralizing CD4bs mAbs, b13 and m18, but it displayed no reactivity to four CD4bs mAbs that do not neutralize primary HIV-1 isolates, nor with mAbs directed to other regions of the HIV-1 Env, including the coreceptor-binding region of gp120 and the V3 and C5 regions of gp120 (FIG. 14, Table S1). DRSC3, which lacked a single amino acid at position 371 that eliminated b12 binding, served as a negative control. Together, these data confirmed the integrity of the antibody binding surface of this resurfaced protein, and it was used for analyses of sera and to identify B cells from an HIV-1-infected individual whose sera contained broadly reactive NAbs.

A panel of broadly neutralizing sera was screened for the presence of antibodies that could preferentially bind to RSC3 compared with DRSC3. CD4bs antibodies were detected in several sera, including serum from donor 45, which had been shown to contain NAbs directed to the CD4bs of gp120 (FIG. 7). To determine whether antibodies that bind to RSC3 were responsible for the broad neutralization mediated by serum 45, neutralization studies were performed by using RSC3 to compete cognate antibodies. The utility of this assay was confirmed with the CD4bs mAb b12 and with mAb F105, which binds differently to the CD4bs and does not bind RSC3 (FIG. 14, Table S1). mAb b12 neutralizes many primary HIV-1 strains, whereas F105 neutralizes mainly laboratory-adapted or other highly sensitive virus strains, such as the HXB2 strain. The addition of RSC3 but not DRSC3 inhibited b12-mediated neutralization of HXB2. RSC3 had no effect on F105 neutralization, and neither RSC3 nor DRSC3 affected neutralization by the anti-V3 mAb 447-52D (FIG. 1D). To interrogate serum 45 neutralization, RSC3 competition studies were performed with this serum against a panel of diverse HIV-1 strains (FIG. 1E). This analysis suggested that serum 45 neutralization was principally directed against the CD4bs on functional viral spikes and that the RSC3 faithfully mimicked this structure.

To isolate CD4bs-directed mAbs, a method of antigen-specific memory B cell sorting was used together with single cell polymerase chain reaction (PCR), to amplify immunoglobulin G (IgG) heavy- and light-chain genes from the cDNA of individual B cells. RSC3 and DRSC3 were expressed with a tagged amino acid sequence that allows biotin labeling. The two proteins could thus be distinguished by fluorescence-activated cell sorting (FACS) analysis after labeling with streptavidin (SA) conjugated to the fluorochromes allophycocyanin (SA-APC) or phycoerythrin (SA-PE), respectively. Peripheral blood mononuclear cells (PBMC) from donor 45 were incubated with RSC3 SA-APC and DRSC3 SA-PE, and single antigen-specific memory B cells were sorted into wells of a microtiter plate after selecting for memory B cells (CD19+, CD20+, and IgG+) that bound to the RSC3 but not the ΔRSC3 probe (FIG. 2A). Out of about 25 million PBMC, 29 single RSC3-specific memory B cells were sorted, and the matching heavy- and light-chain genes were successfully amplified from 12 cells. After cloning into IgG1 expression vectors that reconstituted the heavy and light-chain constant regions, the full IgG mAbs were expressed. Three antibodies (VRC01, VRC02, and VRC03) bound strongly to RSC3 and weakly or not at all to DRSC3 (FIG. 2B, left, FIG. 2C, and FIGS. 8 and 9). To confirm the specificity of these antibodies for the CD4bs, enzyme linked immunosorbent assay (ELISA) was used to test the binding of each mAb against a wild-type gp120 and the CD4bs-defective Asp368→Arg368 (D368R) mutant (FIG. 2B, right). VRC01 and VRC02 bound with ≥100-fold lower relative affinity to the heavy chain variable gene (VH) D368R mutant compared with wild-type gp120, and VRC03 showed no detectable binding to the CD4bs knockout mutant. The ELISA binding profile to an extended panel of mutant Env proteins further confirmed the CD4bs specificity of VRC01, VRC02, and VRC03 (FIG. 14, Table S1).

Analysis of the heavy- and light-chain nucleotide sequences using JoinSolver software (joinsolver.niaid.nih.gov) and the Immunogenetics Information System (IMGT) database (imgt.cines.fr) revealed that VRC01 and VRC02 were somatic variants of the same IgG1 clone. The heavy-chain CDR3 region of both mAbs was composed of the same 14 amino acids (FIG. 10), and both mAbs were highly somatically mutated, with 32% of the heavy chain variable gene (VH) and 17 to 19% of the kappa light chain variable gene (VK) nucleotides divergent from putative germline gene sequences. VRC03 was potentially derived from a different IgG1 clone, but its heavy chain was derived from the same IGHV1-02*02 and IGHJ1*01 alleles as VRC01 and VRC02. VRC03 was also highly somatically mutated, with an unusual seven-amino acid insertion in heavy-chain framework 3 and 30% of VH and 20% of VK nucleotides divergent from putative germline gene sequences. The heavy chain CDR3 of VRC03 contained 16 amino acids. All three mAbs share common sequence motifs in heavy-chain CDR1, CDR2, and CDR3.

The binding characteristics of the mAbs were further analyzed by surface plasmon resonance (SPR), competition ELISA, and isothermal titration calorimetry (ITC). SPR demonstrated that VRC01 (KD=3.88×10-9M) and VRC02 (KD=1.11×10-8 M) bound gp120 with high affinity whereas VRC03 reacted with about 10-fold lower affinity (KD=7.31×10-8 M). To evaluate the epitope reactivity of these mAbs on gp120, competition ELISAs was performed with a panel of well-characterized mAbs. As expected, binding by all three VRC mAbs was competed by CD4bs mAbs b12 and F105 and by CD4-Ig (FIG. 3A left and FIG. 11A). Unexpectedly, the binding of mAb 17b to its site in the coreceptor binding region of gp120 was markedly enhanced by the addition of VRC01 or VRC02 (FIG. 3A right). This enhancing effect was similar, although not as profound, as the known effect of CD4-Ig. In contrast, mAb b12 inhibited mAb 17b binding (FIG. 3A right), as previously shown. A similar enhancing result was observed for VRC01 in an assay that measures gp120 binding to its CCR5 coreceptor (FIG. 11C). Thus, VRC01 and VRC02 act as partial CD4 agonists in their interaction with gp120, whereas VRC03 does not display this effect. Thermodynamic analysis by ITC provided data consistent with the ELISA results and demonstrated a change in enthalpy (−DH) associated with the VRC01-gp120 interaction that was similar to the interaction of CD4-Ig and gp120 (FIG. 3B), further demonstrating that VRC01 binding induced conformational changes in gp120. In contrast to the data for gp120 binding, VRC01 did not enhance viral neutralization by mAb 17b (FIG. 12). These data suggest that VRC01 and VRC02 partially mimic the interaction of CD4 with gp120. This may explain their broad reactivity, because essentially all HIV-1 isolates must engage CD4 for cell entry.

The potency and breadth of neutralization by VRC01, VRC02, and VRC03, compared with those by b12 and CD4-Ig, were assessed on a comprehensive panel of Env pseudoviruses (FIGS. 4 and 15-24, Table S2a-S2j). These 190 viral strains represented all major circulating HIV-1 genetic subtypes (clades) and included viruses derived from acute and chronic stages of HIV-1 infection. VRC01 neutralized 91% of these viruses with a geometric mean value of 0.33 mg/ml (FIGS. 4 and 15-24, Table S2a-S2j). The data for VRC02 were very similar (FIGS. 15-24, Table S2a-S2j). Of note, these mAbs were derived from an HIV-1 clade B-infected donor yet displayed neutralization activity against all genetic subtypes of HIV-1. VRC03 was less broad than VRC01 and VRC02, neutralizing 57% of the viruses (FIGS. 15-24, Table S2a-S2j). In contrast, b12, also derived from a clade B-infected donor, neutralized 41% of viruses tested. Because VRC01 was derived from a donor whose sera was also broadly neutralizing, the relationship between the neutralization breadth and potency of serum 45 IgG and mAb VRC01 was also assessed. Among 140 viruses tested, there was a significant association (P=0.005; Fisher's exact test) between the number of viruses neutralized by serum 45 IgG and the number neutralized by VRC01 (FIG. 13A). Among the 122 viruses neutralized by both serum IgG and VRC01, there was a strong association (P<0.0001; Deming linear regression) between the neutralization potency of the serum IgG and the potency of VRC01 (FIG. 13B). Therefore, although VRC01 did not account for all serum 45 IgG neutralization, the VRC01-like antibody specificity largely accounts for the extensive breadth and potency of serum 45. These findings demonstrate that a focused B cell response can target a highly conserved region of the HIV-1 Env in humans.

Other mAbs are able to neutralize HIV-1, but none has a profile of potency and breadth similar to VRC01 and VRC02. Antibody 4E10 requires relatively high concentrations to neutralize primary strains of HIV-1, and it neutralizes only 12% of Env-pseudoviruses at a concentration of less than 1 μg/ml. The well-characterized CD4bs mAb b12 and the more recently described HJ16 are informative with respect to antigen recognition, but each display restricted breadth (˜40% of HIV-1 strains). Recently, two broadly neutralizing somatic variant mAbs, PG16 and PG9, were isolated by high-throughput neutralization screening of B cell supernatants. The PG16 and PG9 neutralized 73% and 79%, respectively, of viruses tested and recognized a glycosylated region of HIV-1 Env that is present on the native viral trimer, but this epitope is not well presented on gp120 or gp140. VRC01 and VRC02 access the CD4bs region of gp120 in a manner that partially mimics the interaction of CD4 with gp120. This observation may explain their impressive breadth of reactivity. The isolation of these mAbs from an HIV-1-infected donor and the demonstration that they neutralize the vast majority of HIV-1 strains by targeting the functionally conserved receptor binding region of Env provides proof of concept that such antibodies can be elicited in humans. The discovery of these mAbs provides new insights into how the human immune system is able to effectively target a vulnerable site on the viral Env.

Materials and Methods

Human Specimens.

The sera and peripheral blood mononuclear cells (PBMC) described in this Example were from HIV-1 infected individuals enrolled in investigational review board approved clinical protocols at the National Institute of Allergy and Infectious Diseases. Donor 45, from whom mAbs VRC01, VRC02 and VRC03 were isolated, has been HIV-1 infected with a clade B virus for more than 15 years. He is a slow progressor with CD4 T-cell counts over 500 cells/μl, plasma HIV-1 RNA values less than 15,000 copies/ml. He has not initiated antiretroviral treatment.

Computational Design of the Antigenically Resurfaced Core (RC) and Resurfaced Stabilized Core (RSC) Proteins.

The atomic level structures of HIV-1 gp120 in complex with CD4 (Protein Data Bank (PDB) ID: 2NXY), b12 (PDB ID: 2NY7), and F105 (PDB ID: 3HI1) defined the CD4-binding footprint, and neutralizing (b12) as well as non-neutralizing (F105) antibody epitopes on gp120. These structures were used to guide the computational design of new gp120 proteins that maintain the b12 neutralizing epitope but modify the antigenic surface outside the b12 epitope. Modifications outside the b12 epitope included, but were not limited to, mutations to eliminate CD4 and F105 binding and trimming the V1/V2 to eliminate co-receptor epitopes. Designs of most of the resurfaced proteins were based on the wild-type HXB2 core in PDB ID: 2NXY to optimize expression and folding. However, since the stabilized core version of gp120 HXB2 Ds12F123 eliminates binding to most non-neutralizing antibodies and keeps b12 binding intact, some designs (including RSC3) were based on the stabilized core version of gp120 HXB2 Ds12F123.

The general algorithm of the resurfacing design is illustrated in FIG. 5A. First, candidate resurfacing positions on gp120 were identified as surface exposed positions that do not contact the antibody (b12) and are not within or near an N-glycosylation site. Next, the set of amino acids allowed at each resurfacing position was assigned semi-automatically, employing a combination of different types of information (evolutionary information, structural and 2 solubility considerations, and similarity/differences with wild-type or pre-existing designs). Finally, ROSETTADESIGN™ was used to select low energy sequences. Different final designs were generated largely by devising different sets of allowed amino acids at each design position, but also by modifying the design positions themselves. The genes of the resurfaced proteins were synthesized for cloning, and the RC and RSC proteins were expressed and characterized for antigenic properties. What follows are details on the process and the individual designs.

Identification of Resurfacing Positions.

CD4- and b12-contacting residues as well as the surface accessibility of each residue on gp120 were determined based on the gp120-CD4 and gp120-b12 structures (PDB ID 2NXY and 2NY7). Surface exposed residues were defined using the program NACCESS (bioinf.manchester.ac.uk/naccess) as residues with >40% side-chain surface area exposed, relative to the same side-chain in an isolated tripeptide. Antibody contact residues were defined as any gp120 residue with at least one heavy atom within 8.0 angstroms of a heavy atom on the antibody. Residues near N-glycosylation sites were defined as any residue with at least one side-chain heavy atom within 6.0 angstroms of any heavy atom on either the Nacetyl-glucosamine (NAG) group or the asparagine of a N-glycosylation site (NXS/T, where X is any residues except proline). Initially, 49 candidate positions were identified on b12-bound gp120 (PDB ID: 2NY7), but the above criteria were relaxed in some cases to allow additional design positions, and in other cases design positions were restricted to generate pairs of molecules with resurfacing mutations at complementary sets of positions.

Semi-Automatic Assignment of Amino Acid Libraries.

Different strategies were used to assign libraries of allowed amino acids at each resurfacing position, in order to obtain different final sequences from ROSETTADESIGN™. For the design of RSC2, amino acids from a multiple sequence alignment of HIV-1 HXB2 with SIV (hiv.lanl.gov) were allowed (evolutionary information), but most hydrophobic residues were disallowed unless packed on the surface of a beta sheet, and all polar and the native HIV-1 residues were allowed (structural and solubility considerations). RC1 was derived from RSC2 by threading the final RSC2 sequence onto the CD4-bound structure (2NXY) and reverting mutations that would destabilize the CD4-bound conformation. The design of RSC3 was carried out following experimental feedback that RSC2 successfully maintained nM b12 affinity. For RSC3, most mutations from RSC2 were enforced, a wider range of amino acids were allowed at some positions that had not been mutated in RSC2, and additional resurfacing positions were selected based on both exposure and distance from mutations in RSC2. The goal was to ensure that as many potential antibody footprints of area ˜20 A2 outside the b12-binding site as possible contained at least one mutation. The criteria for resurfacing positions were relaxed for RSC3—eight of the new positions were near a NAG, and six were slightly less than 40% exposed. Finally, the native amino acid was not allowed at the new RSC3 design positions, guaranteeing increased resurfacing surface coverage. Resurfacing positions and allowed amino acids for RC4-8 were designed to increase the resurfaced area and antigenic diversity of RC1, following experimental feedback that RC1 maintained high b12 affinity. RC8 was generated using an expanded set of design positions and nearly only polars were allowed at all design positions. RC7 was generated using the same design positions as RC8, but the amino acids chosen for RC8 were disallowed at most design positions, and native amino acids were disfavored directly by assigning them a small energetic penalty. RC4 and RC5 utilized different resurfacing positions compared to RC1, RC7, and RC8 wherever possible, were restricted to polar mutations, and RC5 was designed to be antigenically different than RC4 by disallowing amino acids chosen for RC4. RC6 used the same design positions as RC1, but expanded beyond those positions, and disallowed the amino acids used in RC1.

ROSETTADESIGN™ Parameters.

In all cases non-exposed amino acids were held fixed at the native rotamer. In most cases surface exposed amino acids that were kept as native were also held fixed at the native rotamer. For design of RSC3, amino acids designed into the parent RSC2 were allowed to repack during design of RSC3. The lowest energy design for a particular combination of resurfacing positions and allowed amino acids was selected for experimental testing.

RSC2 and RSC3 Sequences.

The final RSC2 and RSC3 designs contained 34 and 61 mutations relative to the stabilized core (HXB2 Ds12F123) in PDB ID: 2NY7, respectively (not including the V1/V2 trim discussed below). The stabilized core has a total of 330 amino acids, so the resurfacing mutations in RSC2 and RSC3 amounted to modifications of 10% and 18% of the protein, respectively. For RSC3, 82% (50/61) of the mutations were contained in the SIV multiple sequence alignment and 18% (11/61) were not, illustrating that structural and solubility considerations contributed to the design. Only 11 (18%) of the final RSC3 mutations were 4 contained within the sequence of SIVmac32H, illustrating the importance of using a multiple sequence alignment rather than a single sequence. Mutations for all the resurfaced proteins are highlighted in the sequence alignment in FIG. 5B.

Eliminating CD4 and F105 Binding.

RSC2 and RSC3 were designed on the stabilized core that already eliminates F105 binding. To eliminate CD4 binding, the resurfacing described above was expected to suffice due to mutations of two CD4 contact residues in the β20/21 (mutations were N425G and W427V) and due to the favored b12-bound conformation of the β20/21 over the bridging sheet conformation necessary for CD4 binding (by mutations in β20/21 and in al which is linked to β2021 by a disulfide in RSC3). To eliminate F105-binding for RC1 and RC4-8 mutations at key F105 contact locations were added to the resurfacing design. To eliminate CD4 binding for RC1 and RC4-8, the β20/21 was truncated to GG between 1423 and Y435.

V1/V2 Stem Trimming.

The V1/V2 was trimmed differently in different constructs, attempting to find minimal truncation while maintaining high protein expression. RSC2 utilized the same V1/V2 trim as the stabilized core in the b12-crystal structure (PDB ID: 2NY7), but RSC3 had a more aggressively truncated V1/V2 (see alignment in FIG. 5B). RC1 and RC4-8 used a V1/V2 trim sequence of VKLTPLAGATSVITQA (SEQ ID NO. 1466) between C119 and C205.

Protein Expression and Purification.

Genes for HXB2 core, the stabilized core (HXB2 Ds12F123) and the designed RC and RSCs were each synthesized with a C-terminal His tag by GeneArt (Regensburg, Germany), and cloned into a mammalian CMV/R expression vector. Proteins were produced by transient tranfection using 293fectin (Invitrogen, Carlsbad, Calif.) in 293F cells, a human embryonic kidney cell line (Invitrogen) maintained in serum-free free-style medium (Invitrogen). Culture supernatants were harvested 4-5 days after transfection, filtered through a 0.45 μm filter, and concentrated with buffer-exchange into 500 mM NaCl, 50 mM Tris (pH 8.0). Proteins were first purified by Co-NTA (cobalt-nitrilotriacetic acid) chromatography method using a HiTrap IMAC HP column (GE Healthcare, Piscataway, N.J.). The peak fractions were collected, and further purified by gel-filtration using a HiLoad 16/60 Superdex 200 pg column (GE Healthcare). The fractions containing monomers of each protein were combined, concentrated and flash frozen at −80° C. To generate the surface plasmon resonance (SPR) data 5 shown in FIG. 2C and FIGS. 8 and 9, both RSC3 and the stabilized core (Ds12F123) were further purified using b12 affinity column. Monomeric gp120s were expressed by transient transfection of 293F cells.

Surface Plasmon Resonance (SPR).

The binding kinetics of gp120 variants with different ligands were assessed by SPR analysis on Biacore 3000 or Biacore T-100 (GE Healthcare). HIV6 1 gp120-reactive ligands (CD4-Ig and specific mAbs) were either immobilized directly onto a CMS sensor chip with standard amine coupling or captured with a mouse anti-human IgG Fc antibody supplied in the “human antibody capture kit” (GE Healthcare) to a surface density about 300 response units (RU). Variant gp120s at 5-200 nM were first passed over the modified sensor chips at 30 μI/min for 3-4 minutes, followed by a 5 minutes dissociation phase to identify rough binding affinities. Then a 2-fold increasing series of gp120 concentrations were passed over the chip, with the concentration of the series adjusted so that at least three runs resulted in maximum 10-150 RU.

Accompanying each gp120 series, blank reference using buffer to mock gp120 was included. The buffer in all studies was 10 mM HEPES, pH 7.4, 150 mM NaCl, 3 mM EDTA, and 0.01% surfactant P-20. Sensorgrams were corrected with blank reference and fit globally with Biacore Evaluation software using a 1:1 Langmuir model of binding. Although CD4-Ig and other ligands might formally be analyzed with a two-state binding model, such treatment should not affect the primary on-rates nor overall KDs reported here.

ELISA Analyses.

Each antigen in PBS (pH 7.4) at 2 μg/ml was used to coat plates overnight at 4° C. Coated plates were blocked with B3T buffer (150 mM NaCl, 50 mM Tris-HCl, 1 mM EDTA, 3.3% fetal bovine serum, 2% bovine albumin, 0.07% Tween 20) for 1 hour at 37° C., followed by incubation with sera or antibody serially diluted in B3T buffer for 1 hour at 37° C. Horseradish peroxidase (HRP)-conjugated goat anti-human IgG Fc antibody (Jackson ImmunoResearch Laboratories Inc., West Grove, Pa.) at 1:10,000 was added for 1 hour at 37° C. All volumes were 100 μl/well except that 200 μl/well was used for blocking. Plates were washed between each step with 0.1% Tween 20 in PBS. Plates were developed using either 3,3′,5,5′-tetramethylbenzidine (TMB) (Kirkegaard & Perry Laboratories) and read at 450 nm, or ophenylenediamine dihydrochloride (Sigma) and read at 490 nm. For competitive ELISA analyses, plates were coated with 1 μg/ml of a sheep anti-gp120 C5 antibody, D7324 (Cliniqa Corp., Fallbrook, Calif.) or 10 μg/ml of Galanthus nivalis lectin (Sigma) to capture 2 μg/ml of purified YU2 gp120 or RSC3 respectively. After blocking, serial dilutions of the competitor antibodies or CD4-Ig were added to the captured gp120 or RSC3 in 50 μl of B3T buffer, followed by adding 50 μl of biotin-labeled antibody at fixed concentrations: 100 ng/ml for VRC01 and VRC02 for both proteins, 4 μg/ml for VRC03 for YU2 gp120 or 100 ng/ml for RSC3, and 20 ng/ml for 17b for YU2 gp120. The plates were incubated at 37° C. for 1 hour, followed by incubation with 250 7 ng/ml of streptavidin-HRP (Sigma) at ambient temperature for 30 minutes, and developed with TMB as described.

Isothermal Titration Calorimetry (ITC).

Isothermal titration calorimetry (ITC) was carried out using ITC200 microcalorimeter system from MicroCal, Inc. All proteins were thoroughly dialyzed against PBS before use. The dialysis buffer was filtered through a 0.2 μm membrane and used to dilute the protein samples. The concentration of gp120 in the sample cell was approximately 5 μM and that of CD4-Ig or mAbs in the syringe was approximately 25 μM. The molar concentrations of the proteins were calculated using the following molar extinction coefficients: gp120, 1.52; CD4-Ig, 1.2; b12, 1.46; VRC01, 1.53; VRC03, 1.57. Gp120 in the sample cell were titrated to saturation by the stepwise addition of 2 μl of ligand from the syringe at 120-sec intervals at 37° C. The heat evolved upon each injection was obtained from the integral of the calorimetric signal. The values for enthalpy (AH) and entropy (AS) were obtained by fitting the data to a nonlinear least-squares analysis with Origin software.

Viral Entry, Neutralization and Protein Competition Assays.

Neutralization was measured using single round infection by HIV-1 Env-pseudoviruses and TZM-bl target cells. Neutralization curves were fit by nonlinear regression using a 5-parameter hill slope equation. The 50% and 80% inhibitory concentrations (IC50 and IC80) were reported as the antibody concentrations required to inhibit infection by 50% and 80% respectively. Competition of serum or mAb neutralization was assessed by adding a fixed concentration (25 μg/ml) of the RSC3 or ΔRSC3 glycoprotein to serial dilutions of antibody for 15 min prior to the addition of virus. The resulting IC50 values were compared to the control with mock protein added. The neutralization blocking effect of the proteins was calculated as the percent reduction in the IC50 value of the antibody in the presence of protein compared to PBS. Synergistic or additive neutralization was assessed by mixing a fixed concentration (10 μg/ml) of the test antibody with serial dilutions of sCD4, CD4-Ig or VRC01 for 15 min prior to the addition of virus. The baseline of viral entry at each concentration of sCD4, CD4-Ig or VRC01 was used to calculate the adjusted percent neutralization. Neutralization was also assessed 8 using Env-pseudoviruses generated by 293T transfection using the pNL4-3 ΔEnv HIV-1 backbone containing a luciferase reporter gene to infect activated PBMC. Neutralizations using uncloned PBMC-derived HIV-1 primary isolates were performed by single-round infection of either TZM-bl cells using luciferase as readout, or activated PBMC using flow cytometry staining for HIV-1 p24 antigen. CD4-facilitated virus entry was performed in the CCR5+/CD4− cell line Cf2Th/syn CCR5 with Env-pseudoviruses containing the luciferase pNL4-3 ΔEnv HIV-1 backbone. A mixture of 40 μl of viral stock and 10 μl of serial dilutions of sCD4, CD4-Ig or VRC01 was incubated at 37° C. for 30 min before adding 1×104 Cf2Th/syn CCR5 cells. Virus entry was measured 2 days later by luciferase activity in cell lysates.

Construction of the HIV-1 Envelope Sequence Dendrogram.

HIV-1 gp160 protein sequences (excluding the signal peptide) of HXB2 and the 190 isolates used in the neutralization assays were aligned using MUSCLE, for multiple sequence comparison by log-expectation. The protein distance matrix was calculated by “protdist” and the dendrogram was constructed using the neighbor-joining method by “Neighbor”. All analysis and the programs used were performed at the NIAID Biocluster (niaid-biocluster.niaid.nih.gov). The tree was displayed with Dendroscope.

Isolation of Antigen-Specific Memory B Cells by Fluorescence Activated Cell Sorting (FACS).

The plasmid constructs for RSC3 and ΔRSC3 were modified by the addition of the sequence encoding the Avi-tag signal for biotinylation (LNDIFEAQKIEWHE, SEQ ID NO: 26) at the 3′ end of the gene, and the modified genes were subcloned into the CMV/R expression vector. After expression and purification, the proteins were biotinylated at 40 μM utilizing biotin ligase Bir A (Avidity, Denver, Colo.) at 30° C. for 30 min, followed by removal of excess free biotin and buffer exchange with PBS (pH 7.4) using a 30-kDa Centricon plus filter (Millipore). Biotinylation of the RSC proteins was confirmed by ELISA. To conjugate proteins with the streptavidin-fluorochrome reagents, in a stepwise process, ⅕ of the molar equivalent of the streptavidin-fluorochrome reagent was added to the biotinylated RSC3 or ΔRSC3 at 20-min intervals until the molar ratio of streptavidin-fluorochrome reagent: biotinylated protein reached 1:1. The incubation was carried out at 4° C. with gentle rocking. Streptavidin-allophycocyanin (SA-APC) (Invitrogen) was 9 mixed with biotinylated RSC3 and streptavidin-phycoerythrin (SA-PE) (Sigma) was mixed with biotinylated ΔRSC3. Thus, each protein carried a different fluorochrome: RSC3-SA-APC and ΔRSC3-SA-PE.

Antigen specific B cells were identified with a panel of ligands including fluorescently labeled antibodies for CD3, CD8, CD19, CD20, CD27, CD14, IgG and IgM. PBMC were stained with an antibody cocktail consisting of anti-CD3-APC-Cy7 (BD Pharmingen), CD8-Qdot705 (VRC), CD19-Qdot585 (VRC), CD20-Pacific Blue (VRC), CD27-APC-AlexaFluor700 (Beckman Coulter), CD14-Qdot800 (VRC), IgG-FITC (BD Pharmingen), and IgM-PE-Cγ5 (BD Pharmingen). In addition, aqua blue (Invitrogen) was used to exclude dead cells. A total of 25 million cryopreserved PBMC were thawed and resuspended in 10 ml RPMI 1640 medium (Invitrogen) with 10% fetal bovine serum pre-warmed to 37° C. and treated with 20 μg/ml DNase I (New England Biolabs, Ipswich, Mass.), followed by centrifugation at 860×G for 5 min. Medium was removed and the cells were resuspended in 10 ml chilled PBS followed by centrifugation at 860×G for 5 min. The cell pellet was resuspended in 50 μl of chilled PBS with the aqua blue dye and stained at 4° C. in dark for 20 min. The antibody cocktail and the RSC3 and ΔRSC3 multimers, in a total volume of 50 μl, was added to the cells and incubated at 4° C. in dark for 1 hour. The cells were washed with 10 ml cold PBS, resuspended in 2 ml cold PBS and passed through a 70-μm cell mesh (BD Biosciences). The stained PBMC were analyzed and sorted using a modified 3-laser FACSAria cell sorter using the FACSDiva software (BD Biosciences). Fluorescence compensation was performed using anti-mouse Ig Kappa compensation beads (BD Biosciences) stained with each antibody in a separate tube. For the CD3-APC-Cy7 antibody, anti-mouse IgH&L COMPtrol beads (Spherotech, Lake Forrest, Ill.) were used and the aqua blue fluorescence was compensated using pre-labeled amine-beads. Single cells with the phenotype of CD3−, CD8−, aqua blue−, CD14−, CD19+, CD20+, IgG+, IgM−, RSC3+ and ΔRSC3− were defined as CD4bs directed antigen specific B cells, and single cells were sorted into 96-well PCR plates containing 20 μl of lysis buffer per well. The lysis buffer contained 0.5 μl of RNase Out (Invitrogen), 5 μl of 5× first strand buffer (Invitrogen), 1.25 μl of 0.1M DTT (Invitrogen) and 0.0625 μl of Igepal (Sigma). The PCR plates with sorted cells were quickly frozen on dry-ice and stored at −80° C. The total content of the patient PBMC sample 10 passing through the sorter was saved in FCS files for further analysis with FlowJo software (TreeStar, Cupertino, Calif.).

Single B-Cell RT-PCR and Subsequent Sequencing and Cloning.

For each sorted cell, the IgG heavy and the corresponding Ig light chain gene transcripts were amplified by RT-PCR and cloned into eukaryotic expression vectors to produce full IgG1 antibodies. The frozen plates with single B-cell RNA were thawed at room temperature, and the RT reaction was carried out by adding 3 μl of random hexamers at 150 ng/μ1, 2 μl of dNTP mix, each at 10 mM, and 1 μl of SuperScript III (Invitrogen) into each well. The thermocycle program for RT was 42° C. for 10 min, 25° C. for 10 min, 50° C. for 60 min and 94° C. for 5 min. The cDNA plates were stored at −20° C., and the IgH, Igκ and Igλ variable region genes were amplified independently by nested PCR starting from 5 μl of cDNA as template. All PCRs were performed in 96-well PCR plates in a total volume of 50 μl containing water, 5 μl of 10× buffer, 1 μl of dNTP mix, each at 10 mM, 1 μl of MgCl2 at 25 mM (Qiagen) for 1st round PCR or 10 μl 5×Q-Solution (Qiagen) for 2nd round PCR, 1 μl of primer or primer mix for each direction at 25 μM, and 0.4 μl of HotStar Taq DNA polymerase (Qiagen). Each round of PCR was initiated at 94° C. for 5 min, followed by 50 cycles of 94° C. for 30 sec, 58° C. for IgH and Igκ or 60° C. for Igλ for 30 sec, and 72° C. for 1 min, followed by 72° C. for 10 min. The positive 2nd round PCR products were cherry-picked for direct sequencing with both forward and reverse PCR primers. PCR products that gave a productive IgH, Igκ or Igλ rearranged sequence were re-amplified from the 1st round PCR using custom primers containing unique restriction digest sites and subsequently cloned into the corresponding Igγ1, Igκ and Igλ expression vectors. The full-length IgG1 was expressed by cotransfection of 293F cells with equal amounts of the paired heavy and light chain plasmids, and purified using a recombinant protein-A column (GE Healthcare).

IgG Gene Family Analysis.

The IgG heavy and light chain nucleotide sequences of the variable region were analyzed with JoinSolver (Joinsolver.niaid.nih.gov) and using the IMGT database (imgt.cines.fr). Normal donor peripheral blood data originated from 120 IgD+CD27+ and 97 IgD-CD27+ sequences pooled for heavy chain analysis and 167 mutated IgM+ sequences for kappa chain analysis. The VRC mAb VK gene use was 11 determined by homology to germline genes in the major 2p11.2 IGK locus. VRC mAb D gene use was determined by homology to genes in the major 14q32.33 IGH locus.

Env and CCR5 Cell Surface Staining.

293T cells were transfected with plasmid DNA encoding JRFL Env to express the envelope glycoprotein on the cell surface. Cells were stained with anti-Env mAbs. The FACS signal was generated by adding a secondary antibody, goat anti-human IgG F(ab′)2 conjugated with phycoerythrin (SouthernBiotech), at 1:125. Data were collected using flow cytometry with the BD LSR Flow Cytometer, and binding curves were generated by plotting the mean fluorescence intensity (MFI) as a function of antibody concentration. To assess gp120 binding to CCR5 on the surface of cells, biotinylated gp120 was used at 5 μg/ml to stain the CCR5 expressing canine thymus cell line, Cf2Th/syn CCR5. Prior to the staining of Cf2Th/syn CCR5 cells, biotinylated gp120 was incubated with ligands including CD4-Ig, VRC01, VRC02, VRC03 and b12 at serial concentrations ranging from 0.04-25 μg/ml. A streptavidin-APC conjugate (Invitrogen) was used at 1 μg/ml to stain Cf2Th/syn CCR5 cells to generate FACS signal, and binding data were collected using flow cytometry with the BD LSR Flow Cytometer. All the staining and incubations were carried out at room temperature for 1 hour.

Statistical analysis.

Statistical analyses were performed using GraphPad Prism version 5.0 (GraphPad Software Inc.). A two-sided Fisher's Exact Test at alpha=0.05 was used for assessing the relationship between the viral sensitivity to serum 45 IgG and to VRC01. Among the viruses that were sensitive to both, Deming Regression was used to model the relationship on the log 10 scale, allowing for measurement error in the IC50s for both the serum IgG and the mAb. These models were run under the assumption of equal error variance. As a sensitivity analysis, the regression models were rebuilt with an estimated variance ratio; although the slope estimate changed slightly, the conclusions were consistent.

The amino acid sequences of the heavy and light chains of VRC01, VRC02 and VRC03 are shown below (SEQ ID NOs: 1-4, 27 and 28). Bold residues indicate the locations of the CDRs. Exemplary nucleic acid sequences encoding the heavy and light chains of VRC01, VRC02 and VRC03 (SEQ ID NOs: 29-34) are also shown below.

VRC01 Heavy Chain (SEQ ID NO: 1):  QVQLVQSGGQMKKPGESMRISCRASGYEFIDCTLNWIRLAPGKRPEWMGW LKPRGGAVNYARPLQGRVTMTRDVYSDTAFLELRSLTVDDTAVYFCTRGK NCDYNWDFEHWGRGTPVIVSS VRC01 Light Chain (SEQ ID NO: 2):  EIVLTQSPGTLSLSPGETAIISCRTSQYGSLAWYQQRPGQAPRLVIYSGS TRAAGIPDRFSGSRWGPDYNLTISNLESGDFGVYYCQQYEFFGQGTKVQV DIKR VRC02 Heavy Chain (SEQ ID NO: 3):  QVQLVQSGGQMKKPGESMRISCQASGYEFIDCTLNWVRLAPGRRPEWMGW LKPRGGAVNYARPLQGRVTMTRDVYSDTAFLELRSLTADDTAVYYCTRGK NCDYNWDFEHWGRGTPVTVSS VRC02 Light Chain (SEQ ID NO: 4):  EIVLTQSPGTLSLSPGETAIISCRTSQYGSLAWYQQRPGQAPRLVIYSGS TRAAGIPDRFSGSRWGPDYNLTIRNLESGDFGLYYCQQYEFFGQGTKVQV DIKR VRC03 Heavy Chain (SEQ ID NO: 27):  QVQLVQSGAVIKTPGSSVKISCRASGYNFRDYSIHWVRLIPDKGFEWIGW IKPLWGAVSYARQLQGRVSMTRQLSQDPDDPDWGVAYMEFSGLTPADTAE YFCVRRGSCDYCGDFPWQYWGQGTVVVVSS VRC03 Light Chain (SEQ ID NO: 28):  EIVLTQSPGILSLSPGETATLFCKASQGGNAMTWYQKRRGQVPRLLIYDT SRRASGVPDRFVGSGSGTDFFLTINKLDREDFAVYYCQQFEFFGLGSELE VH VRC01 Heavy Chain (SEQ ID NO: 29):  CAGGTGCAGCTGGTGCAGTCTGGGGGTCAGATGAAGAAGCCTGGCGAGTC GATGAGAATTTCTTGTCGGGCTTCTGGATATGAATTTATTGATTGTACGC TAAATTGGATTCGTCTGGCCCCCGGAAAAAGGCCTGAGTGGATGGGATGG CTGAAGCCTCGGGGGGGGGCCGTCAACTACGCACGTCCACTTCAGGGCAG AGTGACCATGACTCGAGACGTTTATTCCGACACAGCCTTTTTGGAGCTGC GCTCGTTGACAGTAGACGACACGGCCGTCTACTTTTGTACTAGGGGAAAA AACTGTGATTACAATTGGGACTTCGAACACTGGGGCCGGGGCACCCCGGT CATCGTCTCATCACC VRC01 Light Chain (SEQ ID NO: 30):  GAAATTGTGTTGACACAGTCTCCAGGCACCCTGTCTTTGTCTCCAGGGGA AACAGCCATCATCTCTTGTCGGACCAGTCAGTATGGTTCCTTAGCCTGGT ATCAACAGAGGCCCGGCCAGGCCCCCAGGCTCGTCATCTATTCGGGCTCT ACTCGGGCCGCTGGCATCCCAGACAGGTTCAGCGGCAGTCGGTGGGGGCC AGACTACAATCTCACCATCAGCAACCTGGAGTCGGGAGATTTTGGTGTTT ATTATTGCCAGCAGTATGAATTTTTTGGCCAGGGGACCAAGGTCCAGGTC GACATTAAGCGA VRC02 Heavy Chain (SEQ ID NO: 31):  CAGGTGCAGCTGGTGCAGTCTGGGGGCCAGATGAAGAAGCCTGGCGAGTC GATGAGAATTTCTTGTCAGGCTTCCGGATATGAATTTATTGATTGTACAC TAAATTGGGTTCGCCTGGCCCCCGGAAGAAGGCCTGAATGGATGGGATGG CTGAAGCCTCGAGGGGGGGCCGTCAACTACGCACGTCCACTTCAAGGCAG AGTGACCATGACTCGAGACGTGTATTCCGACACAGCCTTTTTGGAGCTGC GCTCCTTGACAGCAGACGACACGGCCGTCTACTATTGTACTAGGGGAAAA AATTGTGATTACAATTGGGACTTCGAACACTGGGGCCGGGGTACCCCGGT CACCGTCTCATCA VRC02 Light Chain (SEQ ID NO: 32):  GAAATTGTGTTGACACAGTCTCCAGGCACCCTGTCTTTGTCTCCAGGGGA AACAGCCATCATCTCTTGTCGGACCAGTCAGTATGGTTCCTTAGCCTGGT ATCAACAGAGGCCCGGCCAGGCCCCCCGGCTCGTCATCTATTCGGGCTCT ACTCGGGCCGCAGGCATCCCAGACAGGTTCAGCGGCAGTCGGTGGGGGCC AGACTACAATCTCACCATCAGGAACCTGGAGTCGGGAGATTTTGGTCTTT ATTATTGCCAGCAGTATGAATTTTTTGGCCAGGGGACCAAGGTCCAGGTC GACATTAAGCGA VRC03 Heavy Chain (SEQ ID NO: 33):  CAGGTGCAGCTGGTGCAGTCTGGGGCTGTGATTAAGACGCCTGGGTCCTC AGTGAAGATCTCATGTCGGGCTTCTGGATACAACTTTCGTGATTATTCGA TCCATTGGGTCCGCCTCATTCCTGACAAGGGATTTGAGTGGATTGGATGG ATTAAACCTCTGTGGGGTGCCGTCAGTTATGCCCGGCAACTTCAGGGCCG AGTCTCTATGACTCGACAATTATCTCAAGACCCAGACGACCCGGACTGGG GCGTTGCCTACATGGAGTTCAGTGGACTGACGCCCGCCGACACGGCCGAA TATTTTTGTGTCCGGAGAGGGTCCTGTGATTATTGCGGAGACTTTCCCTG GCAATACTGGGGTCAGGGCACCGTCGTCGTCGTCTCGTCA VRC03 Light Chain (SEQ ID NO: 34):  GAAATTGTGTTGACGCAGTCTCCCGGCATCCTGTCTCTGTCTCCAGGAGA GACAGCCACCCTCTTTTGTAAGGCCAGTCAGGGTGGCAATGCTATGACGT GGTATCAGAAGAGACGTGGCCAGGTTCCCAGACTCCTGATCTACGATACA TCTCGCAGGGCCTCTGGCGTTCCTGACAGATTTGTTGGCAGTGGGTCTGG GACAGACTTCTTTCTCACGATCAACAAATTGGACCGGGAAGATTTCGCAG TCTATTATTGTCAACAATTTGAATTTTTTGGCCTGGGGAGCGAGCTGGAA GTCCATCGA

Example 2 Characterization of the Atomic Structure of VRC01 and gp120

This example describes the crystal structure for one of the VRC01 antibody in complex with an HIV-1 gp120 core. As disclosed herein the molecular basis of VRC01 neutralization is deciphered. In addition the mechanisms of natural resistance of HIV are identified and it shown how VRC01 minimizes such resistance.

To gain a structural understanding of VRC01 neutralization the antigen-binding fragment (Fab) of VRC01 was crystallize in complex with an HIV-1 gp120 from the clade A/E recombinant 93TH057. The crystallized gp120 consisted of its inner domain-outer domain core, with truncations in the variable loops V1/V2 and V3 as well as the N- and C-termini, which are regions known to extend away from the main body of the gp120 envelope glycoprotein. Diffraction to 2.9 Å resolution was obtained from orthorhombic crystals, which contained four copies of the VRC01-gp120 complex per asymmetric unit, and the structure was solved by means of molecular replacement and refined to a crystallographic R value of 19.7% (FIG. 26 and FIG. 47, Table S1).

The interaction surface between VRC01 and gp120 encompasses almost 2500 Å2, with 1244 Å2 contributed by VRC01 and 1249 Å2 by gp120. On VRC01, both heavy chain (894 Å2) and light chain (351 A2) contribute to the contact surface (FIG. 48, Table S2), with the central focus of binding on the heavy chain-second complementarity-determining region (CDR H2). Over half of the interaction surface of VRC01 (644 Å2) involves CDR H2, a mode of binding that is reminiscent of the interaction between gp120 and the CD4 receptor; CD4 is a member of the V-domain class of the immunoglobulin superfamily, and the CDR2-like region of CD4 is a central focus of gp120 binding (FIG. 27A and FIG. 49, Table S3). For CD4, the CDR2-like region forms antiparallel, intermolecular hydrogen bonds with residues 365gp120 to 368gp120 of the CD4-binding loop of gp120 (FIG. 27B); with VRC01, one hydrogen bond is observed between the carbonyl oxygen of Gly54VRC01 and the backbone nitrogen of Asp368gp120. This hydrogen bond occurs at the loop tip, an extra residue relative to CD4 is inserted in the strand, and the rest of the potential hydrogen bonds are of poor geometry or distance (FIG. 27C and FIG. 50, Table S4). Other similarities and differences with CD4 are found: Of the two dominant CD4 residues (Phe43CD4 and Arg59CD4) involved in interaction with gp120, VRC01 mimics the arginine interaction but not the phenylalanine one (FIGS. 27, B and C). Lastly, substantial correlation was observed between gp120 residues involved in binding VRC01 and CD4 (FIG. 32).

Superposition of the gp120 core in its VRC01-bound form with gp120s in other crystalline lattices and bound by other ligands indicates a CD4-bound conformation [Protein Data Bank (PDB) ID number 3JWD] to be most closely related in structure, with a Ca-root-mean-square deviation of 1.03 Å (FIG. 51, Table S5). Such superposition of gp120s from CD4- and VRC01-bound conformations brings the N-terminal domain of CD4 and the heavy chain-variable domain of VRC01 into close alignment (FIG. 27), with 73% of the CD4 N-terminal domain volume overlapping with VRC01. This domain overlap is much higher than observed with the heavy chains of other CD4-binding-site antibodies, such as b12, b13, or F105 (FIG. 52, Table S6). However, when the VRC01 heavy chain is superimposed—on the basis of conserved framework and cysteine residues—on CD4 in the CD4-gp120 complex, clashes are found between gp120 and the entire top third of the VRC01 variable light chain (FIG. 27D). In its complex with gp120, VRC01 rotates 43° relative to the CD4-defined orientation and translates 6 Å away from the bridging sheet, to a clash-free orientation that mimics many of the interactions of CD4 with gp120, although with considerable variation. Analysis of electrostatics shows that the interaction surfaces of VRC01 and CD4 are both quite basic, although the residue types of contacting amino acids are distinct (FIG. 33). Thus, although VRC01 mimics CD4 binding to some extent, considerable differences are observed.

When CD4 is placed into an immunoglobulin context by fusing its two N-terminal domains to a dimeric immunoglobulin constant region, it achieves reasonable neutralization. VRC01, however, neutralizes more effectively (FIG. 28A). To understand the structural basis for the exceptional breadth and potency of VRC01, its interactive surface with gp120 was analyzed. VRC01 focuses its binding onto the conformationally invariant outer domain, which accounts for 87% of the contact surface area of VRC01 (FIG. 53, Table S7). The 13% of the contacts made with flexible inner domain and bridging sheet are noncontiguous, and it was noted that these were not critical for binding. In contrast, CD4 makes 33% of its contacts with the bridging sheet, and many of these interactions are essential. The reduction in inner domain and bridging sheet interactions by VRC01 is accomplished primarily by a 6 Å translation relative to CD4, away from these regions; critical contacts such as made by Phe43CD4 to the nexus of the bridging sheet-outer domain are not found in VRC01, whereas those to the outer domain (such as Arg59CD4) are mimicked by VRC01.

To determine the affinity of VRC01 for gp120 in CD4-bound and non-CD4-bound conformations, surface-plasmon resonance spectroscopy was used to measure the affinity of VRC01 and other gp120-reactive antibodies and ligands to two gp120s: a b4-deletion that is restrained from assuming the CD4-bound conformation or a disulfidestabilized gp120 core that is largely fixed in the CD4-bound conformation in the absence of CD4 itself (FIG. 28B and FIG. 34). VRC01 showed high affinity to both CD4-bound and non-CD4-bound conformations, which is a property shared by the broadly neutralizing b12 antibody. In contrast, antibodies F105 and 17b as well as soluble CD4 showed strong preference for either one, but not both, of the conformations. To assess the binding of VRC01 in the context of the functional viral spike, its ability to neutralize variants of HIV-1 with gp120 changes that affect the ability to assume the CD4-bound state was examined. Two of these mutations, His66Ala gp120 and Trp69Leugp120, are less sensitive, whereas a third, Ser375Trpgp120, is more sensitive to neutralization by CD4. VRC01 neutralized all three of these variant HIV-1 viruses with similar potency (FIG. 28C), suggesting that VRC01 recognizes both CD4-bound and non-CD4-bound conformations of the viral spike. This diversity in recognition allows VRC01 to avoid the conformational masking that hinders most CD4-binding-site ligands and to potently neutralize HIV-1. Precise targeting by VRC01. Prior analysis of effective and ineffective CD4-binding-site antibodies suggested that precise targeting to the vulnerable site of initial CD4 attachment is required to block viral entry. This site represents the outer domain contact for CD4. Analysis of the VRC01 interaction with gp120 shows that it covers 98% of this site (FIGS. 29, A and B, and FIG. 35), comprising 1089 Å2 on the gp120 outer domain, which is about 50% larger than the 730 Å2 surface covered by CD4. The VRC01 contact surface outside the target site is largely limited to the conformationally invariant outer domain and avoids regions of conformational flexibility. This concordance of binding is much greater than for ineffective CD4-binding-site antibodies as well as for those that are partially effective, such as antibody b12 (FIG. 35). The outer domain-contact site for CD4 is shielded by glycan. Contacts by the VRC01 light chain (Tyr28VRC01 and Ser30VRC01) are made with the protein-proximal N-acetylglucosamine from the N-linked glycan at residue 276gp120. Thus instead of being occluded by glycan, VRC01 makes use of a glycan for binding. Other potential glycan interactions may occur with different strains of HIV-1 because the VRC01 recognition surface on the gp120-outer domain extends further than that of the functionally constrained CD4 interaction surface, especially into the loop D and the often-glycosylated V5 region (FIG. 36).

In addition to conformational masking and glycan shielding, HIV-1 resists neutralization by antigenic variation. To understand the basis of this natural resistance to VRC01, 17 resistant isolates were analyzed all by threading their sequences onto the gp120 structure (FIG. 36). Variation was observed in the V5 region in resistant isolates, and this variation along with alterations in gp120 loop D appeared to be the source of most natural resistance to VRC01 (FIG. 29C and FIGS. 36 and 37).

Because substantial variation exists in V5, structural differences in this region might be expected to result in greater than 10% resistance. The lower observed frequency of resistance suggests that VRC01 employs a recognition mechanism that allows for binding despite V5 variation. Examination of VRC01 interaction with V5 shows that VRC01 recognition of V5 is considerably different from that of CD4 (FIG. 38), with Arg61VRC01 in the CDR H2 penetrating into the cavity formed by the V5 and b24 strands of gp120 (FIG. 39). The V5 loop fits into the gap between heavy and light chains; thus, by contacting only the more conserved residues at the loop base, VRC01 can tolerate variation in the tip of the V5 loop (FIG. 29D).

Examination of the structure of VRC01 was conducted for special features that might be required for its function. A number of unusual features were apparent, including a high degree of affinity maturation, an extra disulfide bond, a site for N-linked glycosylation, a two-amino-acid deletion in the light chain, and an extensively matured binding interface between VRC01 and gp120 (FIG. 30 and FIG. 40). The frequency with which these features were found in HIV-1 Env-reactive antibodies or in human antibody-antigen complexes was assessed (FIG. 41, FIG. 54, Table S8 and FIG. 55, Table S9) and measured the effect of genomic reversion of these features on affinity for gp120 and neutralization of virus (FIG. 30, A to D, and FIGS. 56 and 57, Table S10).

Higher levels of affinity maturation have been reported for HIV-1-reactive antibodies in general and markedly higher levels for broadly neutralizing ones. These maturation levels could be a by-product of the persistent nature of HIV-1 infection and may not represent a functional requirement. Removal of the N-linked glycosylation or the extra disulfide bond, which connects CDR H1 and H3 regions of the heavy chain, had little effect on binding or neutralization (FIGS. 30, A and B, and FIGS. 56 and 57, Table S10). Insertion of two amino acids to revert the light chain deletion had moderate effects, which were larger for an Ala-Ala insertion (50-fold decrease in binding affinity) versus a Ser-Tyr insertion (fivefold decrease in affinity), which mimics the genomic sequence (FIG. 30C and FIGS. 56 and 57, Table S10). Lastly, reversion of the interface was examined with either single-, four-, seven- or 12-mutant reversions. For the single-mutant reversions of the interface to the genomic antibody sequence, all 12 mutations had minor effects [most with a less than two-fold effect on the dissociation constant (Kd), with the largest effect for a Gly54Ser change having a Kd of 20.2 nM] (FIGS. 56 and 57, Table S10). Larger effects were observed with multiple (four, seven, or 12) changes (FIG. 30D and FIGS. 56 and 57, Table S10). Thus, although VRC01 has a number of unusual features, no single alteration to genomic sequence substantially altered binding or neutralization.

The probability for elicitation of a particular antibody is a function of each of the three major steps in B cell maturation: (i) recombination to produce nascent antibody heavy and light chains from genomic VH-D-J and Vk/I-J precursors, (ii) deletion of auto-reactive antibodies, and (iii) maturation through hypermutation of the variable domains to enhance antigen affinity. For the recombination step, a lack of substantial CDR L3 and H3 contribution to the VRC01-gp120 interface (FIG. 48, Table S2) indicates that specific Vk/1-J or VH(D)J recombination is not required (FIG. 42). The majority of recognition occurs with elements encoded in single genomic elements or cassettes, suggesting that specific joining events between them are not required. Within the VH cassette, a number of residues associated with the IGHV1-02*02 precursor of VRC01 interact with gp120; many of these are conserved in related genomic VHs, some of which are of similar genetic distance from VRC01 (FIGS. 43 and 44). These results suggest that appropriate genomic precursors for VRC01 are likely to occur at a reasonable frequency in the human antibody repertoire.

Recombination produces nascent B cell-presented antibodies that have reactivities against both self and nonself antigens. Those with autoreactivity are removed through clonal deletion. With many of the broadly neutralizing antibodies to HIV-1, such as 2G12 (glycan reactive) (33, 34), 2F5, and 4E10 (membrane reactive), this appears to be a major barrier to elicitation. Although this remains to be characterized for genomic revertants and maturation intermediates, no autoreactivity has so far been observed with VRC01.

The third step influencing the elicitation of VRC01-like antibodies is affinity maturation, which is a process that involves the hypermutation of variable domains combined with affinity-based selection that occurs during B cell maturation in germinal centers. In the case of VRC01, 41 residue alterations were observed from the genomic VH gene and 25 alterations from the Vk gene (including a deletion of two residues) (FIG. 45). To investigate the effect of affinity maturation on HIV-1 gp120 recognition, the VH and Vk regions of VRC01 were reverted, either individually or together, to the sequences of their genomic precursors. The affinity and neutralization of these reverted antibodies was tested (FIG. 31A) and this data was combined with the genomic reversion data obtained while querying the unusual molecular features of VRC01 (FIG. 31B). No antibodies containing VH and Vk regions, which were fully reverted to their genomic precursors, bound gp120 or neutralized virus. Binding affinity and neutralization showed significant correlations with the number of affinity matured residues (P<0.0001). Binding to stabilized gp120 did not correlate well with other types of gp120 or to neutralization (FIG. 58, Table 511), which is related in part to greater retention of binding to VRC01 variants with genomically reverted Vk regions. Extrapolation of the correlation to the putative genomic V gene sequences predicted binding affinities of 0.7 T 0.4 mM Kd for gp120 stabilized in the CD4-bound conformation and substantially weaker affinities for nonstabilized gp120s (FIG. 31B and FIG. 46).

No single affinity maturation alteration appeared to affect affinity by more than ten-fold, suggesting that affinity maturation occurs in multiple small steps, which collectively enable tight binding to HIV-1 gp120. When the effects of VRC01 affinity maturation reversions are mapped to the structure of the VRC01-gp120 complex, they are broadly distributed throughout the VRC01 variable domains rather than focused on the VRC01-gp120 interface. Noncontact residues therefore appear to influence the interface with gp120 through indirect protein-folding effects. Thus, for VRC01 the process of affinity maturation entails incremental changes of the nascent genomic precursors to obtain high-affinity interaction with the HIV-1 Env surface. Receptor mimicry and affinity maturation. The possibility that antibodies use conserved sites of receptor recognition to neutralize viruses effectively has been pursued for several decades. The recessed canyon on rhinovirus that recognizes the unpaired terminal immunoglobulin domains of intercellular adhesion molecule-1 highlights the role that a narrow canyon entrance may play in such occlusion of bivalent antibody combining regions, although framework recognition can in some instances permit entry. Partial solutions such as those presented by antibody b12 (neutralization of ˜40% of circulating isolates) or by antibody HJ16 (neutralization of ˜30% of circulating isolates), a recently identified CD4-binding-site antibody, may allow recognition of some HIV-1 isolates.

Materials and Methods

Expression and Purification of HIV-1 gp120 Proteins.

The codon-optimized plasmid pVRC8400-HIV-1 Clade A/E 93TH057 4V123 contains gp120 residues 44-492 with specific deletions at the V1/V2 and V3 regions. The expression construct was made by inserting mouse interleukin-2 (IL-2) leader sequence (MYSMQLASCVTLTLVLLVN, SEQ ID NO: 36) followed by the modified gp120 sequence between the 5′ XbaI and 3′ BamHI sites. In the modified gp120 sequence, N-term residues 31-43 of wild type Clade A/E 93TH057 gp120 were trimmed, amino acids sequences ¹²⁴PLCVTLHCTTAKLTNVTNITNVPNIGNITDEVRNCSFNMTTEIRDKKQKVHALFYKLDIVQIED KN DSSKYRLINCNT¹⁹⁸ (SEQ ID NO: 37) of the V1/V2 loop and ³⁰²NMRTSMRIGPGQVFYRTGSIT³²³ (SEQ ID NO: 38) of the V3 loop were replaced with GG and GGSGSG (SEQ ID NO: 39) linkers, respectively. YU2 Δβ4 core gp120 was constructed with YU2 gp120 sequence by replacing the 9 residues of β3-β5 loop with a Gly-Gly linker. This deletion weakens the binding of CD4 and prohibits formation of the antibody 17b epitope. The 93TH057, YU2Δβ4 core gp120 and HXBc2 Ds12F123 core gp120 were expressed and purified. Briefly 1 L of HEK 293 GnTi- or 293 FreeStyle cells were transiently transfected with the mixture of 500 μg of gp120 DNA plasmid and 1 ml of 293fectin (Invitrogen). The transfected cells were incubated in FreeStyle 293 expression medium (Invitrogen) supplemented with 3% Cell Boost (HyClone) and 2 mM Butyrate (SIGMA) for suspension culture at 8% CO2, 37.0° C. and 125 rpm for five days after transfection. The supernatants for 93TH057 and HXBc2 Ds12F123 5 core gp120 were harvested and proteins purified with a protein A-immobilized 17b antibody affinity column. The YU2Δβ4 core gp120 was purified with a protein A-immobilized F105 antibody affinity column. The gp120 proteins were eluted with IgG elution buffer (Pierce) and immediately adjusted to pH 7.5.

Production of VRC01 IgG and Antigen-Binding Fragment.

The VRC01 IgG was expressed and purified. Briefly, heavy and light chain plasmids were transfected into 293F cells using 293Fectin (Invitrogen). The supernatant was harvested 5 days after transfection, filtered through 0.45 μm filter, and followed by purification using immobilized protein A or protein G columns. To produce antigen-binding fragments (Fab), VRC01 IgG was incubated at 37° C. with protease Lys-C(Roche) at a ratio IgG:LysC=4000:1 (w/w) in 10 mM EDTA, 100 mM Tris/Cl—, pH 8.5 for about 12 hours. Uncleaved IgG and the constant fragment (Fc) were removed by passing the digestion mixture through a Protein A affinity column; the flowthrough containing VRC01 Fab was concentrated and loaded onto size-exclusion column (Superdex 5200) for further purification.

Deglycosylation, Complex Formation and Crystallization of the gp120:VRC01 Complexes.

Deglycosylation of HIV-1 gp120 was performed in a reaction solution containing 1-5 mg/ml gp120, 350 mM NaCl, 100 mM Na Acetate, pH 5.9, lx EDTA-free protease inhibitor (Roche) and endoglycosidase H (30 units/μg of gp120). After mixing all components and adjusting pH to 5.9, the solution was incubated at 37° C. and the deglycosylation process was monitored by SDS-PAGE until completion. gp120:VRC01 complexes were made. Briefly, VRC01 Fab in 20% molar excess was combined with deglycosylated gp120 and the gp120:VRC01 mixture was passed through a concanavalin A column to remove gp120 with uncleaved N-linked glycans. The complex was then purified by size exclusion chromatography (Hiload 26/60 Superdex 5200 prep grade, GE Healthcare) and concentrated to ˜10 mg/ml in 0.35 M NaCl, 2.5 mM Tris pH 7.0, 0.02% NaN3 for crystallization screening studies. To achieve better chances of crystallization hits, two gp120 variants, clade B HxBc2 core Ds12F123 and clade A/E 93TH057, were used to make complexes with the VRC01 Fab. Commercially available screens, Hampton Crystal Screen (Hampton Research), Precipitant Synergy Screen (Emerald BioSystems), and Wizard Screen (Emerald BioSystems), were used for initial crystallization trials of the gp120:VRC01 complexes. Vapor-diffusion sitting drops were set up robotically by mixing 0.1 μl of protein with an equal volume of precipitant solutions (Honeybee, DigiLab). Droplets were allowed to equilibrate at 20° C. and imaged at scheduled times with RockImager (Formulatrix.). Multiple crystal hits were obtained from both HXBc2:VRC01 and 93TH057:VRC01 complexes. Those hits were optimized manually using the hanging drop vapor-diffusion method. Crystals of the HXBc2:VRC01 complex were obtained in 1.0 M NaCitrate, 100 mM NaCacodylate, pH 6.5. For the 93TH057:VRC01 complex, the best condition to obtain diffraction-quality crystals was 10% PEG 8000, 100 mM Tris/Cl—, pH 8.5 with 3% glucose as additive.

X-Ray Data Collection, Structure Determination and Refinement for the gp120:VRC01 Complex.

The diffraction of gp120:VRC01 crystals were tested under cryogenic conditions. To search for the best cryo-protectant, protecting effects of six commonly used cryoprotectants, 30% glycerol, 30% ethylene glycol, 15% 2R,3R-butanediol, 40% trihalose, 40% sucrose and 40% glucose, were assessed. Crystals were transferred into solutions which were composed of crystallization reservoir solution with 50% higher concentration of precipitant(s) and each individual cryo-protectant or mixture of cryoprotectants, immediately flash frozen in liquid nitrogen with a cryo-loop (Hampton Research) and mounted under cryo condition (100K°) for data collection. X-ray data were collected at beam-line ID-22 (SER-CAT) at the Advanced Photon Source, Argonne National Laboratory, with 0.82656 Å radiation, processed and reduced with HKL2000). None of the HXBc2:VRC01 crystals diffracted beyond 4 Å resolution and they were not used for data collection. A 2.9 Å data set for the 93TH057:VRC01 crystals was collected using a cryoprotectant solutions containing 15% PEG8000, 100 mM Tris/Cl—, pH 8.5 and 20% glucose and 7.5% 2R,3R-butanediol as cryoprotectants. I/σ ratio was 1.2 at the 2.9 Å shell with 68% completeness. The crystal structure of the 93TH057:VRC01 complex was solved by molecular replacement with Phaser in the CCP4 Program Suite. This crystal belonged to a space group P21 with cell dimensions a=108.6, b=98.3, c=205.3, β=99.7 and contained four molecules per asymmetric unit. The structure of 93TH057 gp120 with β20/β21 region trimmed (PDB #3M4M) was used as an initial model to place the gp120 in the complex. Phaser was able to give a solution with three gp120s initially (RFZ=4.3 TFZ=4.7 PAK=0 LLG=69 8 RFZ=3.5 TFZ=11.8 PAK=0 LLG=234 RFZ=3.7 TFZ=17.5 PAK=0 LLG=485 LLG=1280). With those three gp120s fixed, the CDR-loop-trimmed variable domain (Fv) of antibody b13 (PDB ID 3IDX) was used to locate the Fv portion of VRC01 in the complex (RFZ=3.7 TFZ=11.7 PAK=0 LLG=539 RFZ=3.9 TFZ=5.0 PAK=0 LLG=389 RFZ=3.9 TFZ=4.7 PAK=0 LLG=136 LLG=428). Visual inspection of the generated gp120:Fv solutions identified one of gp120s complexed with a symmetry-operated Fv. This new gp120:Fv complex was used as model to perform a new round of molecular replacement, one complex at a time, until all four gp120:Fv complexes were found (Round 1: RFZ=6.6 TFZ=8.9 PAK=0 LLG=72 LLG=243, Round 2: RFZ=5.9 TFZ=16.0 PAK=0 LLG=78 LLG=623, Round 3: RFZ=8.4 TFZ=25.3 PAK=0 LLG=739 LLG=1866, Round 4: RFZ=5.8 TFZ=22.8 PAK=0 LLG=990 LLG=2608). The constant domain of Fab b13 was then used to place one of the VRC01 constant domains with all four previous solutions fixed (RFZ=4.7 TFZ=21.5 PAK=1 LLG=1357 LLG=3313). The newly found constant domain and the gp120:Fv formed a complete gp120:VRC01 complex and the other three molecules were generated by superposing this complex with other three gp120s in the asymmetric unit. Further refinement was carried out with PHENIX. Starting with torsion-angle simulated annealing with slow cooling, iterative manual model building was carried out on Xtalview and COOT with maps generated from combinations of standard positional, individual B-factor, TLS refinement algorithms and non-crystallographic symmetry (NCS) restraints. Ordered solvents were added during each macro cycle. Throughout the refinement processes, a cross validation (Rfree) test set consisting of 5% of the data was used. Structure validations were performed periodically during the model building/refinement process with MolProbity and pdb-care. Even though the reported data at the highest shell of 2.9 Å only has I/σ ratio of 1.2, reflections up to 2.7 Å resolution (I/σ>1.0, ˜30% completeness) were included and used during the refinement. Xray crystallographic data and refinement statistics are summarized in FIG. 47, Table 51.

Surface Plasmon Resonance (SPR).

The binding kinetics of HIV-1 gp120 with different ligands were performed on Biacore 3000 or Biacore T-100 (GE Healthcare) at 20° C. with buffer HBS-EP+ (10 mM HEPES, pH 7.4, 150 mM NaCl, 3 mM EDTA, and 0.05% surfactant P-20). To assess VRC01 recognition of gp120 in the CD4-bound and non-CD4-bound conformation, gp120 molecules (YU2Δβ4 core and HXBc2 Ds12F123 core) were immobilized onto a CMS chip to 250-500 response units (RUs) with standard amine coupling; Fab antibodies, CD4 or CD4-IgαTP at 2-fold increasing concentrations were injected over the gp120 channels at a flow rate of 30 μl/min for 3 minutes and allowed to dissociate for another 5-10 minutes before regeneration with two 25 μl injections of 4.5 M MgCl2 at a flow rate of 50 μl/ml. To test the effects of mutations on VRC01, IgG variants were captured with a mouse anti-human IgG Fc antibody supplied in the “human antibody capture kit” (GE Healthcare) to a surface density about 300 RUs. gp120 series with 2-fold increasing concentrations were passed over the captured IgG flow channels for 3 minutes and allowed to dissociate for another 5-10 minutes at a flow rate of 30 μl/min. The sensor chip was regenerated after each experiment using two 25 μl injections of 4.5 M MgCl2 at a flow rate of 50 μl/ml. Sensorgrams were corrected with appropriate blank references and fit globally with Biacore Evaluation software using a 1:1 Langmuir model of binding. Sensorgrams of IgG b12 binding to gp120 could not be fitted with 1:1 Langmuir model and were analyzed with a 10 two-state binding model; such treatment should not affect the primary on-rates nor overall KDs reported here.

Mutagenesis and Creation of VRC01 Genomic Revertants.

Single-4-, 7-, 12-revertant mutations to germline residues of VRC01 as well as the heavy chain C32SC98A mutations, light chain insertions with Ala-Ala or Ser-Tyr after position 30 were listed in FIG. 59, Table S12 and the mutagenesis were carried out using Quikchange kit (Stratagene) according to manufacturer's protocol. V-gene revertants for VRC01 were constructed as follows: For heavy chain Vgene revertant (gH), VRC01 heavy chain V-gene region was reverted to its germline precursor IGHV 1-02*02. For light chain V-gene revertant (gL), VRC01 light chain Vgene region was reverted to its germline precursor IGKV 3-11*01. The modified heavy and light chain genes were synthesized by GeneArt (Regensburg, Germany), and cloned into a mammalian CMV/R vector for expression. All the VRC01 variants were expressed with the same protocol as wild type VRC01 IgG.

Neutralization Assays.

Neutralization Assays of Viruses by VRC01 and its Variants:

HIV-1 Env-pseudoviruses were prepared by transfecting 293T cells (6×10⁶ cells in 50 ml growth medium in a T-175 culture flask) with 10 μg of rev/env expression plasmid and 30 μg of an env-deficient HIV-1 backbone vector (pSG3ΔEnvelope), using Fugene 6 transfection reagents (Invitrogen). Pseudovirus-containing culture supernatants were harvested two days after transfection, filtered (0.45 μm), and stored at −80° C. or in the vapor 11 phase of liquid nitrogen. Neutralization was measured using HIV-1 Env-pseudoviruses to infect TZM-bl cells as described previously. Briefly, 40 μl of virus was incubated for 30 min at 37° C. with 10 μl of serial diluted test antibody in duplicate wells of a 96-well flat bottom culture plate. To keep assay conditions constant, sham media was used in place of antibody in specified control wells. The virus input was set at a multiplicity of infection of approximately 0.01, which generally results in 100,000 to 400,000 relative light units (RLU) in a luciferase assay (Bright Glo, Promega, Madison, Wis.). The antibody concentrations were defined at the point of incubation with virus supernatant. Neutralization curves were fit by nonlinear regression using a 5-parameter hill slope equation. The 50% inhibitory concentrations (IC50) were reported as the antibody concentrations required to inhibit infection by 50%.

Neutralization Assay of Viruses with Altered Sampling of the CD4-Bound State by VRC01 and CD4.

Recombinant HIV-1 expressing the firefly luciferase gene was produced by calcium phosphate transfection of 293T cells with the molecular clone pNL4.3 (Env−) Luc and the pSVIIIenv plasmid expressing the wild-type or mutant HIV-1YU2 envelope glycoproteins at a weight ratio of 2:1. Two days after transfection, the cell supernatants were harvested. The reverse transcriptase activities of all virus preparations were measured. Each virus preparation was frozen and stored in aliquots at −80° C. until use. Luciferase-expressing viruses bearing either wild-type or mutant envelope glycoproteins were incubated for 1 hour at 37° C. with serial dilutions of sCD4 or VRC01 IgG in a total 12 volume of 200 μl. The recombinant viruses were then incubated with Cf2Th-CD4/CCR5 cells; luciferase activity in the cells was measured two days later.

ELISA Assay.

Clade A/E 93TH057 and clade B HXBc2 core Ds12F123 gp120 in PBS (pH 7.4) at 2 μg/ml were used to coat plates for 2 hours at room temperature (RT). The plates were washed five times with 0.05% Tween 20 in PBS (PBS-T), blocked with 300 μl per well of block buffer (5% skim milk and 2% bovine albumin in PBS-T) for 1 hour at RT. 100 μl of each monoclonal antibodies 5-fold serially diluted in block buffer were added and incubated for 1 hour at RT. Horseradish peroxidase (HRP)-conjugated goat anti-human IgG (H+L) antibody (Jackson ImmunoResearch Laboratories Inc., West Grove, Pa.) at 1:5,000 was added for 1 hour at RT. The plates were washed five times with PBS-T and then developed using 3,3′,5,5′-tetramethylbenzidine (TMB) (Kirkegaard & Perry Laboratories) at RT for 10 min. The reaction was stopped by the addition of 100 μl N H2504 to each well. The readout was measured at a wavelength of 450 nm. All samples were performed in triplicate.

Analysis of the Commonality of VRC01 Features.

Structural Dataset for Analysis of Antibody Affinity Maturation:

Initially, the IMGT/3Dstructure-DB was searched for structures of human antibody-protein and antibody-peptide complexes of at most 3.5 Å resolution. This resulted in a set of 54 antibody-protein and 66 antibody-peptide structures (the 2wuc complex was found in both the protein and peptide databases). To complement the structure query, the RSCB PDB was searched for “human fab complex” and structure resolution of at most 3.5 Å, resulting in a set of 290 structure hits; 211 of these had not been identified as part of the IMGT/3Dstructure-DB search. All unique pdbs from the IMGT/3Dstructure-DB database and the PDB search were manually inspected. Additionally, two structures (2b4c and 3hi1, see FIG. 58, Table S11) not found in either search were also inspected. To be included in the affinity maturation analysis, pdbs had to possess the following properties: antibody-protein or antibody-peptide complex, IgG antibody of human origin, natural affinity maturation, and antigen not artificially modified for improved binding. In the cases where multiple complexes of the same antibody were identified, only one such complex was used for the analysis. As a result, only 26 of the complexes, shown in FIGS. 56 and 57, Table S10, were retained for the antibody affinity maturation analysis. The list of discarded pdbs, along with the specific reasons for discarding, is shown in FIG. 58, Table S11. For each of the selected 26 antibody complexes, the number of antibody contact residues that were mutated from germline was computed for the antibody V-segments. Contact residues were identified using PISA. Antibody germline genes were identified with IgBLAST (ncbi.nlm.nih.gov/igblast) using antibody protein sequences for the search; insertions/deletions were not counted toward the number of mutations from germline. A summary of the number of contact residues, V-segment mutated residues, and mutated contact residues for the 26 antibodies are shown in FIGS. 56 and 57, Table S10.

Analysis of Cys Residues, Residue Deletions, and Glycan Additions:

A dataset of human HIV-1 antibody heavy and light chain sequences was obtained. The final curated version of that dataset that excluded non-specific gp140 14 binders as well as sequences with non-fully-resolved variable regions, included 147 heavy and 147 light chain sequences. Sequence alignment to germline was performed using IMGT/V-QUEST. The number of glycans was computed for the V-D-J heavy and V-J light regions. The number of Cys residues was computed for the V-D-J heavy regions only. The number of residue deletions was computed for the V-segments as compared to the corresponding germline; a deletion of multiple consecutive amino acids was counted as a single deletion.

Numbering of amino acid residues in antibody the Kabat nomenclature for amino acid sequences in antibodies was followed.

Protein structure analysis and graphical representations GRASP and APBS were used in calculations of molecular surfaces, volumes, and electrostatic potentials. PISA was used to perform protein-protein interfaces analysis. CCP4 was used for structural alignments. All graphical representation with protein crystal structures were made with Pymol.

Example 3 2F5 Antibody with Enhanced Neutralization Capacity

The membrane-proximal external region (MPER) of the HIV-1 gp41 transmembrane glycoprotein is the target of three broadly neutralizing anti-HIV-1 antibodies, 2F5, Z13e, and 4E10, and is thus a potential site of HIV-1 vulnerability to the humoral immune response. The MPER encompasses ˜25 residues at the carboxyl-terminal end of the predicted gp41 ectodomain, just before the transmembrane region, and is rich in aromatic residues, typical of bilayer-interfacial regions of membrane proteins. Mutation of selected MPER tryptophans abrogates gp41-mediated fusion of the viral and target cell membranes, indicating that this region is crucial for HIV-1 infectivity. Structural studies of unbound forms of the gp41 MPER both in solution and in lipid contexts have demonstrated that it adopts a number of conformations, many of which are _-helical, and electron-paramagnetic resonance measurements have indicated lipid bilayer immersion depths for MPER residues that range from acyl to phospholipid headgroup regions. The binding of neutralizing antibodies, such as 2F5, to the MPER must therefore account for the membrane milieu in which the epitope is found.

The 2F5 antibody has been shown to exhibit ˜100-fold enhanced binding to its epitope on uncleaved gp140s when presented in the context of lipid proteoliposomes, and other studies have shown that 2F5 can contact phospholipids directly in the absence of gp41. The latter finding has led to the suggestion that 2F5 might be autoreactive, although passive transfusion of 2F5 does not appear to have deleterious effects and 2F5 failed to react in some clinically based assays for autoreactive lipid antibodies. The crystal structures of the 2F5 antibody in complex with its gp41 MPER epitope revealed that, despite the 22-residue length of the 2F5 heavy chain third complementarity-determining region (CDR H3) loop, contacts with the gp41 MPER peptide are made predominantly at the loop base. In some crystal structures, the tip of the loop protrudes away from gp41, while in others, it is disordered. A unique feature of the tip of the CDR H3 loop is that it contains a patch of hydrophobic residues, including residues L100A, F100B, V100D, and I100F (Kabat numbering), which, with the exception of I100F, do not contact gp41 (FIG. 62). While a prior study revealed the importance of residue F100B of the CDR H3 loop in 2F5-neutralizing activity, nonconservative residue substitutions at this position also appeared to diminish 2F5 binding to the immobilized MPER peptide and gp41 in enzyme-linked immunosorbent assay (ELISA) formats. Conversely, a more recent study has shown that alanine mutations in the 2F5 CDR H3 loop can affect neutralization without affecting gp41 binding

As disclosed herein the role of the chemical nature of residues at the tip of the 2F5 CDR H3 loop in neutralization of HIV-1 is examined. Mutations were introduced into the 2F5 CDR H3 loop that altered its hydrophobicity, and the resulting 2F5 mutants were tested both for binding to a gp41 epitope peptide and for neutralization of HIV-1. The results showed that the tip of the 2F5 CDR H3 loop, and specifically its hydrophobic nature, is required for 2F5-mediated neutralization of HIV-1 by means that appear to be independent both of gp41 affinity and of isolate specific sensitivity to neutralization by 2F5.

Materials and Methods

Antibodies.

The heavy and light chains of the 2F5 antibody were codon optimized for mammalian expression, synthesized, and transferred separately into the pVRC8400 (CMV/R) mammalian expression vector. Mutations within the 2F5 CDR H3 loop were analyzed for structural compatibility with neighboring residues and were then introduced into the 2F5 heavy-chain plasmid using standard site-directed mutagenesis techniques, implemented by ACGT, Inc., Chicago, Ill. The wild-type and mutant 2F5 heavy- and light-chain plasmids were transiently transfected into 293 Freestyle cells using 293fectin (Invitrogen), and supernatants containing secreted IgGs were harvested 72 to 96 h posttransfection. The IgGs were purified by flowing the supernatants over a protein A-agarose column (Pierce), followed by elution with IgG elution buffer (Pierce).

Peptides.

A wild-type gp41 MPER peptide corresponding to residues 657 to 669 of gp41 (HxB2 numbering) linked to a C-terminal C9 tag was used and was comprised of the sequence EQELLELDKWASLGGTETSQVAPA (SEQ ID NO: 40)(American Peptide).

Surface Plasmon Resonance.

Biacore 3000 (GE Healthcare) was used in tests. 2F5 wild-type and mutant IgGs were coupled directly to Biacore CMS chips at final densities of ˜4,000 to 5,000 response units (RU). The gp41 MPER peptide was used as the analyte and flowed over at 2-fold serial dilutions ranging from 500 to 0.49 nM at a flow rate of 30 μl/min for 3 min, followed by injection of standard Biacore HEPES buffer (10 mM HEPES, pH 7.4, 150 mM NaCl, 3 mM EDTA, 0.01% P-20) for 3 min. Binding profiles were analyzed using either Biaevaluation software (GE Healthcare) or Scrubber version 2 (Biologic).

Virus Neutralization Assays.

A single-cycle infectivity assay using Envpseudotyped virus and Tzm-bl target cells (NIH AIDS Research and Reference Reagent Program) was used to assess the neutralization capacities of the 2F5 variants. Env from the HIV-1 strains MN, HxB2, JR-FL, SC422661.8, RHPA4259.7, and TRO.11 were used, as were Env from the HIV-2 strain 7312a and the HIV-2-HIV-1 chimera 7312a-Cl. Murine leukemia virus (MuLV) Env was used as a negative control.

Hydrophobicity Analysis.

Analysis of the free energies of partitioning the 2F5 CDR H3 loop tip into octanol or a lipid bilayer interface was performed using MPex 3.1 software (blanco.biomol.uci.edu/mpex). The analysis was performed on residues 100A to 100F of the 2F5 CDR H3 loop using the Totalizer function, with no end groups added and the ACONH value set at 0.

Statistical Analysis.

Statistical analyses were performed using GraphPad Prism version 5.0 (GraphPad Software Inc.) and Origin 7 (Originlab Corporation).

Results

Predictive measures of hydrophobicity, as determined by scales of free energy for partitioning whole residues from water to a lipid bilayer interface, ΔG_(wif), or to octanol, ΔG_(oct), were used to design mutations that would either disrupt or augment the predicted partitioning of the 2F5 CDR H3 tip (residues L100A to I100F) (FIG. 62). The amino acid serine, which is found midway on the ΔG_(wif) and ΔG_(oct) hydrophobicity scales, was chosen as a single or double substitution in order to achieve a gradual decrease in hydrophobicity (FIG. 62C and FIG. 63, Table 1). Conversely, tryptophan, which is the residue most favored to partition into the bilayer interface or octanol, was used to augment the hydrophobicity of the loop (FIG. 62C and FIG. 63, Table 1).

To ascertain the effect of the CDR H3 tip mutations on binding of 2F5 to the gp41 MPER, the affinities of the expressed 2F5 variants for a gp41 MPER peptide were determined using surface plasmon resonance. The 2F5 wild-type and mutant IgGs were coupled directly to the biosensor surface, and a gp41 MPER peptide comprised of residues 657 to 669 of gp41 (isolate HxB2 numbering) linked to a C-terminal C9 tag was used as analyte, at 2-fold serial dilutions ranging from 500 to 0.49 nM. As shown in FIG. 63, Table 1 (FIG. 72), all of the mutants maintained nanomolar affinity to the gp41 peptide. In some cases, such as for mutants of HOOF, there was a moderate reduction in affinity, likely due to minor contacts made by this residue with gp41.

The 2F5 mutants were then tested for neutralization of the laboratory-adapted strain HxB2, which is highly sensitive to wild-type 2F5. A single-cycle infectivity assay using Env-pseudotyped virus and Tzm-bl target cells was employed for this purpose. As shown in FIG. 64, top, even single replacements of hydrophobic residues of the CDR H3 loop with serine were able to reduce the neutralization capacity of 2F5 against HxB2 by several orders of magnitude. The most noticeable single mutation effect was observed for the F100BS mutation, which led to a more than 500-fold increase in the 50% inhibitory concentration (IC50) relative to wild-type 2F5 (FIG. 64, top, and FIG. 63, Table 1). The single mutations L100AS and I100FS likewise led to 100-fold increases in the IC50s, while the V100DS mutation increased the IC50 by about 15-fold. Introduction of double mutations to serine at the same residue locations, furthermore, led to complete abrogation of 2F5-mediated neutralization of HxB2, with neutralization profiles indistinguishable from those of the negative control mouse 1D4 anti-rhodopsin antibody (FIG. 64, middle, CDR H3 loop can reduce and completely disrupt 2F5 neutralization, despite maintaining nanomolar affinity for gp41.

Since these findings could be the result either of a disruption of specific protein contacts made by these residues or of a disruption of nonspecific interactions mediated by their chemical nature, mutation of the same CDR H3 residues to tryptophan was undertaken. Substitutions to tryptophan served two purposes: first, they augmented the hydrophobicity and predicted favorability of free energies of transfer from water to a bilayer interface or to octanol (ΔG_(wif) and ΔGoct), and second, the bulky nature of the tryptophan side chain had the potential to disrupt protein-protein contacts, should they exist. When tested for neutralization of HxB2, the tryptophan mutants were either commensurate with 2F5 wild-type neutralization, such as L100_(A)W and F100_(B)W, or were even more potent, such as V100_(B)W and the double mutant L100_(A)W V100_(D)W, both of which showed an ˜10-fold decrease in the neutralization IC50 relative to wild-type 2F5 (FIG. 64, bottom).

To rule out the possibility that these results were specific to the HxB2 isolate, the 2F5 mutants were tested for neutralization of a panel of tier 1 and tier 2 HIV-1 isolates, ranging from highly sensitive strains, such as MN, to more resistant ones, such as JR-FL, and also to an HIV-2-HIV-1 2F5 epitope chimera, 7312a-Cl. As shown in FIG. 63, Table 1, single mutations that decreased the hydrophobicity of the 2F5 CDR H3 loop led to decreases in neutralization potency, and double mutations that decreased hydrophobicity completely abrogated neutralization. Likewise, single and double mutations that increased the hydrophobicity of the loop led to increased neutralization potencies (FIG. 63, Table 1). Meanwhile, neutralization of the Tro.11 isolate, which has a K665S point mutation in the core of the epitope, was virtually undetectable for all 2F5 mutants, similar to what was observed for viruses pseudotyped with MuLV and parental HIV-2 7312a Env, which were used as negative controls.

To determine if there was a statistical relationship between the hydrophobicity of the 2F5 CDR H3 loop and the neutralization capacity of the antibody, neutralization IC50s of the 2F5 mutants were plotted against the estimated free energies of transfer, ΔG_(wif), of the mutant CDR H3s for each of the strains tested. As shown in FIG. 65A and FIG. 66, Table 2, with the exception of RHPA-4259, statistically significant linear relationships were observed between neutralization IC50s and CDR H3 ΔG_(wif), with P values ranging from 0.0012 for HxB2 to 0.018 for JR-FL. Linear relationships with even more stringent P values were observed between neutralization IC50s and the predicted free energy of transfer to octanol, ΔG_(oct) (FIG. 73A and FIG. 69, Table S1). Associations between the neutralization IC50s and the affinities of the various 2F5 mutants for gp41 MPER peptide were also examined. As shown in FIG. 65B and FIG. 66, Table 2, despite the fact that the fits appear to be largely driven by the KD (dissociation constant) of the I100FS 2F5 mutant for gp41 (which makes minor contacts with the peptide), no statistically significant relationships were observed between the neutralization IC50s of the 2F5 CDR H3 variants and their affinities for the gp41 MPER peptide.

Though the overall levels of the IC50s varied per strain tested, likely a reflection of the strain sensitivity to 2F5 itself, the mutations appeared to exhibit similar effects on neutralization regardless of the strain used. Specifically, no significant differences were observed in the slopes of the linear fits of the neutralization IC50s versus ΔG_(wif) or versus ΔG_(oct), unlike their y intercepts, which did display significant differences (FIG. 65A, and FIG. 66, Table 2). The similarities in the slopes of the regressions across all strains suggested that the neutralization effects mediated by 2F5 CDR H3 loop hydrophobicity were largely independent of strain sensitivity to 2F5. The free energy of antibody neutralization (ΔG^(N)) can be viewed as a sum of free energies that contribute to its functional interactions with a specific strain of virus. It can also be viewed as a binding association of an antibody “n” with the virion: ΔG^(N)−RT ln K(n), where K(n) is defined as IC50/f(n) and f(n) is a function that accounts for variables such as strain sensitivity and assay used. Although an absolute value for this free energy requires the definition of f(n), if f(n1) can be approximated to equal f(n2) for two variants n1 and n2 of the same antibody neutralizing the same strain of virus, a relative free energy, ΔΔG^(N), can be obtained. In the case of 2F5, it was verified how the free energy of partitioning the CDR H3 loop from water to a lipid bilayer interface, ΔG_(wif), or to octanol, ΔG_(oct), correlated with the relative free energy of neutralization (ΔΔG^(N)=ΔG_(2F5wt) ^(N)−ΔG_(2F5mut) ^(N)). Linear models were used to fit curves of ΔΔG^(N) versus ΔG_(wif) (FIG. 65C) or ΔG_(oct) (FIG. 73C) for each individual strain and for all strains together. The shared correlations obtained were statistically significant, with P<0.0001, although end points at high hydrophobicity suggested linear fits might not be ideal (see below). Nonetheless, the results confirmed that the effects of ΔG_(wif) and ΔG_(oct) of the 2F5 CDR H3 loop on virus neutralization were largely independent of the virus strain, with the normalization relative to 2F5 wild type in the ΔΔG^(N)calculation making the fits for all the strains virtually superimposable (FIG. 65C and FIG. 73C). The shared slopes from these correlations were 1.3 and 1.2 for ΔG_(wif) and ΔG_(oct), respectively. Thus, the calculated change in the free energy of partitioning the 2F5 CDR H3 loop translates almost directly into changes in neutralization. The 30% enhancement in neutralization, ΔΔG^(N), over the calculated partition free energy may reflect the planar positioning of these residues in the CDR H3 structure and/or their positioning induced by recognition of the gp41 protein component.

Though linear regressions provided a reasonable first approximation of the relationship between neutralization IC50s and the free energy of hydrophobic transfer of the tip of the 2F5 CDR H3 loop, it was observed that beyond a certain threshold of loop hydrophobicity, the effects on neutralization appeared to level off. To account for this observation, a quadratic term was added to the linear regressions. This yielded better fits of the data, as judged by an extra sums-of-squares F test (FIG. 67A, FIG. 73B and FIG. 70, Table S2). Based on these quadratic models, IC50 minima were interpolated for each of the strains tested (FIG. 71, Table S3). On average, the interpolated minimum IC50s were approximately 0.96 log units or 9.2-fold lower than the corresponding experimental IC50s of wild-type 2F5 (FIG. 71, Table S3). Compared to the interpolated IC50s corresponding to a ΔG_(wif) of 0, in which no transfer is predicted to occur, the mean minimum IC50s were approximately 5.1 log units or 13,000-fold lower than those predicted for a 2F5 variant with no capacity for hydrophobic transfer (FIG. 71, Table S3). A quadratic term was also added to the fits of the plots of the relative free energies of neutralization, ΔΔG^(N), versus the predicted free energies of transfer of the 2F5 CDR H3 loop to a bilayer interface, ΔG_(wif), or octanol, ΔG_(oct) (FIG. 67B and FIG. 77D). Shared quadratic fits of ΔΔG^(N) versus ΔG_(wif) and ΔG_(oct) were also performed, and ΔΔG^(N) minima were observed at 2F5 CDR H3 ΔG_(wif) and ΔG_(oct) values of −4.08 and −5.69 kcal/mol, with corresponding ΔΔG^(N) values of −1.28 and −1.18 kcal/mol, respectively (FIG. 67C and FIG. 77D).

Discussion

The results presented herein suggest that in addition to gp41 MPER binding, interactions mediated by the tip of the 2F5 CDR H3 loop are also required for 2F5-mediated neutralization of HIV-1. For the elements of 2F5-mediated neutralization described here, the free energy of 2F5-mediated virus neutralization, ΔG^(N), can thus be viewed as the sum of the free energy of 2F5 structure-specific recognition of gp41 combined with the free energy of transfer of its CDR H3 loop into a hydrophobic milieu (FIG. 68). While a number of possibilities exist to explain how the tip of the 2F5 CDR H3 mediates neutralization of HIV-1, the finding that mutations to tryptophan were tolerated at three separate locations within the CDR H3 loop, in some cases even augmenting 2F5-mediated neutralization, is consistent with the loop mediating nonspecific hydrophobic interactions. It was surmised that such interactions are more likely to occur at a lipid bilayer interface than within a protein-protein interface, though 2F5 has been shown to tolerate a great deal of sequence variation at its interface with gp41. The finding that correlations of hydrophobicity of the loop and neutralization capacity are largely independent of HIV-1 isolate sensitivity to 2F5, furthermore, suggests that the contacts mediated by the 2F5 CDR H3 loop are distinct from gp41 binding, at least in terms of elements of gp41 not conserved across all strains. The fact that this is true not only for HIV-1 isolates, but also for divergent simian immunodeficiency virus (SIV)-HIV-1 and HIV-2-HIV-1 chimeras, provides additional evidence that 2F5 CDR H3 interactions are not specific for HIV-1 envelope. Because the hydrophobic tip of the CDR H3 represents only a small portion of the surface of antibody 2F5, it seems likely that the reduction in direct binding to lipid vesicles represents an averaging of the alteration in CDR H3 tip hydrophobicity relative to the entire 2F5 antibody. It thus seems reasonable to expect that the full effects of the mutations described herein for neutralization can likely be recapitulated in in vitro lipid binding assays only if the 2F5 CDR H3 loop is properly oriented relative to gp41 and the viral membrane, as it is in the virion/neutralization context, or when the gp41 MPER is presented in a proteoliposome context. The difference between an oriented CDR H3 effect (large and significant) and an overall effect on direct biding to lipid vesicles (weak and less significant) may provide an explanation for the lack of 2F5 autoreactivity in in vivo studies; in the former case, the effect is amplified by the precise orientation of the CDR H3 to the viral membrane through binding to the protein component of the MPER epitope, while in the latter case, the effect is minimized by entropic effects and by averaging over the entire surface of the 2F5 antibody. Finally, it was noted that a number of proteins have interfacial binding properties similar to those proposed for 2F5. Soluble phospholipases A2, for instance, show dramatic interfacial activation of catalytic activity and require attachment to membranes to appropriately position a substrate for catalysis. Such systems may allow additional insight into the neutralization mechanism of 2F5. The sizes and hydrophobicities of likely membrane attachment surfaces, for example, are decreased in neurotoxic phospholipases A2, which need to avoid nonspecific membrane interactions during diffusion to the neuronal synapse. Indeed, quadratic fits of our neutralization versus CDR H3 hydrophobicity data resulted in improved correlations and appeared to reveal a threshold beyond which additional hydrophobicity did not enhance neutralization. Overall, these findings have numerous implications for optimization of 2F5 potency and for recreating 2F5-like antibodies in vaccine settings. Variants of 2F5 with tryptophan substitutions are already ˜10-fold more potent than the wild type in terms of neutralization, and future designs of 2F5-based vaccine immunogens may thus need to account not only for structure-specific recognition of gp41 but also for the hydrophobic interactions mediated by the tip of the 2F5 CDR H3 loop.

2F5 Heavy Chain WT (SEQ ID NO: 5): RITLKESGPPLVKPTQTLTLTCSFSGFSLSDFGVGVGWIRQPPGKALEWL AIIYSDDDKRYSPSLNTRLTITKDTSKNQVVLVMTRVSPVDTATYFCAHR RGPTTLFGVPIARGPVNAMDVWGQGITVTISSTSTKGPSVFPLAPSSKST SGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSV VTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELL GGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVH NAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKT ISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNG QPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNH YTQKSLSLSPGK 2F5 Heavy Chain L_(100A)W (SEQ ID NO: 6): RITLKESGPPLVKPTQTLTLTCSFSGFSLSDFGVGVGWIRQPPGKALEWL AIIYSDDDKRYSPSLNTRLTITKDTSKNQVVLVMTRVSPVDTATYFCAHR RGPTT W FGVPIARGPVNAMDVWGQGITVTISSTSTKGPSVFPLAPSSKST SGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSV VTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELL GGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVH NAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKT ISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNG QPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNH YTQKSLSLSPGK 2F5 Heavy Chain E_(100B)W (SEQ ID NO: 7): RITLKESGPPLVKPTQTLTLTCSFSGFSLSDFGVGVGWIRQPPGKALEWL AIIYSDDDKRYSPSLNTRLTITKDTSKNQVVLVMTRVSPVDTATYFCAHR RGPTTL W GVPIARGPVNAMDVWGQGITVTISSTSTKGPSVFPLAPSSKST SGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSV VTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELL GGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVH NAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKT ISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNG QPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNH YTQKSLSLSPGK 2F5 Heavy Chain V_(100D)W (SEQ ID NO: 8): RITLKESGPPLVKPTQTLTLTCSFSGFSLSDFGVGVGWIRQPPGKALEWL AIIYSDDDKRYSPSLNTRLTITKDTSKNQVVLVMTRVSPVDTATYFCAHR RGPTTLFG W PIARGPVNAMDVWGQGITVTISSTSTKGPSVFPLAPSSKST SGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSV VTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELL GGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVH NAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKT ISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNG QPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNH YTQKSLSLSPGK 2F5 Heavy Chain L_(100A)W-V_(100D)W (SEQ ID NO: 9): RITLKESGPPLVKPTQTLTLTCSFSGFSLSDFGVGVGWIRQPPGKALEWL AIIYSDDDKRYSPSLNTRLTITKDTSKNQVVLVMTRVSPVDTATYFCAHR RGPTT W FG W PIARGPVNAMDVWGQGITVTISSTSTKGPSVFPLAPSSKST SGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSV VTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELL GGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVH NAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKT ISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNG QPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNH YTQKSLSLSPGK 2F5 Light Chain (SEQ ID NO: 10): ALQLTQSPSSLSASVGDRITITCRASQGVTSALAWYRQKPGSPPQLLIYD ASSLESGVPSRFSGSGSGTEFTLTISTLRPEDFATYYCQQLHFYPHTFGG GTRVDVRRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKV DNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYECEVTHQG LSSPVTKSFNRGEC

Example 4 HIV-1 Monoclonal Neutralizing Antibodies Specific to gp120 or gp41 for Detecting HIV-1 in a Subject

This example describes the use of HIV-1 monoclonal neutralizing antibodies specific to gp120 or gp41 for the detection of HIV-1 in a subject. This example further describes the use of these antibodies to confirm the diagnosis of HIV-1 in a subject.

A biological sample, such as a blood sample is obtained from the patient diagnosed with, or suspected of having an HIV-1 infection. A blood sample taken from a patient who is not infected is used as a control. An ELISA is performed to detect the presence of HIV-1 in the blood sample. Proteins present in the blood samples (the patient sample and control sample) are immobilized on a solid support, such as a 96-well plate, according to methods well known in the art (see, for example, Robinson et al., Lancet 362:1612-1616, 2003, incorporated herein by reference). Following immobilization, HIV-1 monoclonal neutralizing antibodies specific to gp120 or gp41 that is directly labeled with a fluorescent marker is applied to the protein-immobilized plate. The plate is washed in an appropriate buffer, such as PBS, to remove any unbound antibody and to minimize non-specific binding of antibody. Fluorescence can be detected using a fluorometric plate reader according to standard methods. An increase in fluorescence intensity of the patient sample, relative to the control sample, indicates the anti-gp120 or gp41 antibody specifically bound proteins from the blood sample, thus detecting the presence of HIV-1 protein in the sample. Detection of HIV-1 protein in the patient sample indicates the patient has HIV-1, or confirms diagnosis of HIV-1 in the subject.

Example 5 HIV-1 Monoclonal Neutralizing Antibodies Specific to gp120 or gp41 for the Treatment of HIV-1

This example describes a particular method that can be used to treat HIV in a human subject by administration of one or more gp120 or gp41 specific human neutralizing mAbs. Although particular methods, dosages, and modes of administrations are provided, one skilled in the art will appreciate that variations can be made without substantially affecting the treatment.

Based upon the teaching disclosed herein HIV-1 can be treated by administering a therapeutically effective amount of one or more of the neutralizing mAbs described herein, thereby reducing or eliminating HIV infection.

Screening Subjects

In particular examples, the subject is first screened to determine if they have HIV. Examples of methods that can be used to screen for HIV include a combination of measuring a subject's CD4+ T cell count and the level of HIV in serum blood levels. Additional methods using the gp120- and gp41-specific mAbs described herein can also be used to screen for HIV.

In some examples, HIV testing consists of initial screening with an enzyme-linked immunosorbent assay (ELISA) to detect antibodies to HIV, such as to HIV-1. Specimens with a nonreactive result from the initial ELISA are considered HIV-negative unless new exposure to an infected partner or partner of unknown HIV status has occurred. Specimens with a reactive ELISA result are retested in duplicate. If the result of either duplicate test is reactive, the specimen is reported as repeatedly reactive and undergoes confirmatory testing with a more specific supplemental test (e.g., Western blot or an immunofluorescence assay (IFA)). Specimens that are repeatedly reactive by ELISA and positive by IFA or reactive by Western blot are considered HIV-positive and indicative of HIV infection. Specimens that are repeatedly ELISA-reactive occasionally provide an indeterminate Western blot result, which may be either an incomplete antibody response to HIV in an infected person, or nonspecific reactions in an uninfected person. IFA can be used to confirm infection in these ambiguous cases. In some instances, a second specimen will be collected more than a month later and retested for subjects with indeterminate Western blot results. In additional examples, nucleic acid testing (e.g., viral RNA or proviral DNA amplification method) can also help diagnosis in certain situations.

The detection of HIV in a subject's blood is indicative that the subject has HIV and is a candidate for receiving the therapeutic compositions disclosed herein. Moreover, detection of a CD4+ T cell count below 350 per microliter, such as 200 cells per microliter, is also indicative that the subject is likely to have HIV.

Pre-screening is not required prior to administration of the therapeutic compositions disclosed herein

Pre-Treatment of Subjects

In particular examples, the subject is treated prior to administration of a therapeutic agent that includes one or more antiretroviral therapies known to those of skill in the art. However, such pre-treatment is not always required, and can be determined by a skilled clinician.

Administration of Therapeutic Compositions

Following subject selection, a therapeutically effective dose of a gp120 or gp41 specific neutralizing mAb described herein is administered to the subject (such as an adult human or a newborn infant either at risk for contracting HIV or known to be infected with HIV). Additional agents, such as anti-viral agents, can also be administered to the subject simultaneously or prior to or following administration of the disclosed agents. Administration can be achieved by any method known in the art, such as oral administration, inhalation, intravenous, intramuscular, intraperitoneal, or subcutaneous.

The amount of the composition administered to prevent, reduce, inhibit, and/or treat HIV or a condition associated with it depends on the subject being treated, the severity of the disorder, and the manner of administration of the therapeutic composition. Ideally, a therapeutically effective amount of an agent is the amount sufficient to prevent, reduce, and/or inhibit, and/or treat the condition (e.g., HIV) in a subject without causing a substantial cytotoxic effect in the subject. An effective amount can be readily determined by one skilled in the art, for example using routine trials establishing dose response curves. As such, these compositions may be formulated with an inert diluent or with an pharmaceutically acceptable carrier.

In one specific example, antibodies are administered at 5 mg per kg every two weeks or 10 mg per kg every two weeks depending upon the particular stage of HIV. In an example, the antibodies are administered continuously. In another example, antibodies or antibody fragments are administered at 50 μg per kg given twice a week for 2 to 3 weeks.

Administration of the therapeutic compositions can be taken long term (for example over a period of months or years).

Assessment

Following the administration of one or more therapies, subjects having HIV can be monitored for reductions in HIV levels, increases in a subjects CD4+ T cell count, or reductions in one or more clinical symptoms associated with HIV. In particular examples, subjects are analyzed one or more times, starting 7 days following treatment. Subjects can be monitored using any method known in the art. For example, biological samples from the subject, including blood, can be obtained and alterations in HIV or CD4+ T cell levels evaluated.

Additional Treatments

In particular examples, if subjects are stable or have a minor, mixed or partial response to treatment, they can be re-treated after re-evaluation with the same schedule and preparation of agents that they previously received for the desired amount of time, including the duration of a subject's lifetime. A partial response is a reduction, such as at least a 10%, at least 20%, at least 30%, at least 40%, at least 50%, or at least 70% in HIV infection, HIV replication or combination thereof. A partial response may also be an increase in CD4+ T cell count such as at least 350 T cells per microliter.

Example 6 Use of Epitope Scaffolds as Immunological Probes

In order to detect and isolate structure specific antibodies against viral neutralizing determinants, use of heterologous epitope scaffolds can be used.

Epitope scaffolds are proteins that are surface engrafted with an epitope of choice in a manner that maintains the desired structural conformation of the epitope. In the case of gp41 epitope scaffolds, the gp41 membrane proximal extracellular region (MPER) target of the broadly neutralizing 2F5 antibody is engrafted onto the surface of heterologous proteins in a manner that preserves its 2F5-bound conformation. Five such scaffolds have been developed thus far using a graft that is derived from a clade B virus. Epitope scaffolds with MPER grafts derived from other clades, such as clades C and A and any other clades or gp41 sequences that should be required, are also included as immunological probes in this disclosure. Point mutations within the grafts which knock out binding to 2F5 are also included for use as negative selection agents—in that isolated antibodies directed against the core of the MPER epitope should not be able to bind to these point mutants.

When used as probes, the gp41 MPER epitope scaffolds are biotinylated as previously described (Doria-Rose, et al, Journal of Virology, January 2009, p. 188-199, Vol. 83, No. 1). An Avitag sequence for biotinylation (LNDIFEAQKIEWHE, SEQ ID NO: 26) is added at the c-terminal end of the scaffold (see sequences below). After expression in either mammalian cells (e.g., 293 freestyle cells, Invitrogen) or in E. coli cells (e.g., BL21 cells, Novagen), Biotin ligase Bir A (Avidity, Denver, Colo.) is used to biotinylate the scaffolds at the Avitag sequence.

Sequences of gp41 MPER Epitope Scaffold Immunological Probes (graft are underlined and in bold):

ES1 (1LGYA)  ES1 (1LGYA) Clade B (SEQ ID NO: 11):  EVLEADKWAILG ATKYAGIAATAYCRSVVPGNKWDCVQCQKWVPDGKIIT TFTSLLSDTNGYVLRSDKQKTIYLVFRGTNSFRSAITDIVFNFSDYKPVK GAKVHAGFLSSYEQVVNDYFPVVQEQLTAHPTYKVIVTGHSLGGAQALLA GMDLYQREPRLSPANLSIFTVGGPRVGNPTFAYYVESTGIPFARTVHKRD IVPHVPPQSFGFLHPGVESWIKSGTSNVQVCGSAIETKDCSNSIVPFTSI LDHLSYFDINEGSCLSGLVPRGSGSHHHHHHGGLNDIFEAQKIEWHE ES1 (1LGYA) Clade B point mutant (SEQ ID NO: 12):  EVLEADEWAILG ATKYAGIAATAYCRSVVPGNKWDCVQCQKWVPDGKIIT TFTSLLSDTNGYVLRSDKQKTIYLVFRGTNSFRSAITDIVFNFSDYKPVK GAKVHAGFLSSYEQVVNDYFPVVQEQLTAHPTYKVIVTGHSLGGAQALLA GMDLYQREPRLSPANLSIFTVGGPRVGNPTFAYYVESTGIPFARTVHKRD IVPHVPPQSFGFLHPGVESWIKSGTSNVQVCGSAIETKDCSNSIVPFTSI LDHLSYFDINEGSCLSGLVPRGSGSHHHHHHGGLNDIFEAQKIEWHE ES1 (1LGYA) Clade C (SEQ ID NO: 13):  EVLALDSWKNLG ATKYAGIAATAYCRSVVPGNKWDCVQCQKWVPDGKIIT TFTSLLSDTNGYVLRSDKQKTIYLVFRGTNSFRSAITDIVFNFSDYKPVK GAKVHAGFLSSYEQVVNDYFPVVQEQLTAHPTYKVIVTGHSLGGAQALLA GMDLYQREPRLSPANLSIFTVGGPRVGNPTFAYYVESTGIPFARTVHKRD IVPHVPPQSFGFLHPGVESWIKSGTSNVQVCGSAIETKDCSNSIVPFTSI LDHLSYFDINEGSCLSGLVPRGSGSHHHHHHGGLNDIFEAQKIEWHE ES2 (1KU2A-s)  ES2 (1KU2A-s) Clade B (SEQ ID NO: 14):  ASDPVRQYLHEIG EVLELDKWAELG AAAKVEEGMEAIKKLSEATGLDQEL IREVVRAKILGTAAIQKIPGLKEKPDPKTVEEVDGKLKSLPKELKRYLHI AREGEAARQHLIEANLRLVVSIAKKYTGRGLSFLDLIQEGNQGLIRAVEK FEYKRGFAFSTYATWWIRQAINRAIADQARSGLVPRGSGSHHHHHHGGLN DIFEAQKIEWHE ES2 (1KU2A-s) Clade B point mutant (SEQ ID NO: 15): ASDPVRQYLHEIG EVLELDEWAELG AAAKVEEGMEAIKKLSEATGLDQEL IREVVRAKILGTAAIQKIPGLKEKPDPKTVEEVDGKLKSLPKELKRYLHI AREGEAARQHLIEANLRLVVSIAKKYTGRGLSFLDLIQEGNQGLIRAVEK FEYKRGFAFSTYATWWIRQAINRAIADQARSGLVPRGSGSHHHHHHGGLN DIFEAQKIEWHE ES2 (1KU2A-s) Clade C (SEQ ID NO: 16):  ASDPVRQYLHEIG EVLALDSWKNLG AAAKVEEGMEAIKKLSEATGLDQEL IREVVRAKILGTAAIQKIPGLKEKPDPKTVEEVDGKLKSLPKELKRYLHI AREGEAARQHLIEANLRLVVSIAKKYTGRGLSFLDLIQEGNQGLIRAVEK FEYKRGFAFSTYATWWIRQAINRAIADQARSGLVPRGSGSHHHHHHGGLN DIFEAQKIEWHE ES3 (2MATA)  ES3 (2MATA) Clade B (SEQ ID NO: 17):  EILELDKWAILG MRVAGRLAAEVLEMIEPYVKPGVSTGELDRICNDYIVN EQHAVSACLGYHGYPKSVCISINEVVCHGIPDDAKLLKDGDIVNIDVTVI KAGAHGDTSKMFIVGKPTIMGERLCRITQESLYLALRMVKPGINLREIGA AIQKFVEAEGFSVVREYCGHGIGGGFHEEPQVLHYDSRETNVVLKPGMTF TIEPMVNAGKKEIRTMKDGWTVKTKDRSLSAQYEHTIVVTDNGCEILTLR KDDTIPAIISHDSGLVPRGSGSHHHHHHGGLNDIFEAQKIEWHE ES3 (2MATA) Clade B point mutant (SEQ ID NO: 18):  EILELDEWAILG MRVAGRLAAEVLEMIEPYVKPGVSTGELDRICNDYIVN EQHAVSACLGYHGYPKSVCISINEVVCHGIPDDAKLLKDGDIVNIDVTVI KAGAHGDTSKMFIVGKPTIMGERLCRITQESLYLALRMVKPGINLREIGA AIQKFVEAEGFSVVREYCGHGIGGGFHEEPQVLHYDSRETNVVLKPGMTF TIEPMVNAGKKEIRTMKDGWTVKTKDRSLSAQYEHTIVVTDNGCEILTLR KDDTIPAIISHDSGLVPRGSGSHHHHHHGGLNDIFEAQKIEWHE ES3 (2MATA) Clade C (SEQ ID NO: 19):  EILALDSWKNLG MRVAGRLAAEVLEMIEPYVKPGVSTGELDRICNDYIVN EQHAVSACLGYHGYPKSVCISINEVVCHGIPDDAKLLKDGDIVNIDVTVI KAGAHGDTSKMFIVGKPTIMGERLCRITQESLYLALRMVKPGINLREIGA AIQKFVEAEGFSVVREYCGHGIGGGFHEEPQVLHYDSRETNVVLKPGMTF TIEPMVNAGKKEIRTMKDGWTVKTKDRSLSAQYEHTIVVTDNGCEILTLR KDDTIPAIISHDSGLVPRGSGSHHHHHHGGLNDIFEAQKIEWHE ES4 (1IWLA)  ES4 (1IWLA) Clade B (SEQ ID NO: 20):  DAASDLKSRLDKVSSFGAGFTQKVTDVQEGQGALAVKRPNLFAWHMTQPD ESILVSDGKTLWFYNPFVEQATATWLKDATGNTPFMLIARNQSSDWQQYN IKQNGDDFVLTPKASNGNLKQFTINVGRDGTIHQFSAVEQDDQRSSYQLK AQ ENLEVDKWAFLF GPPQGVTVDDQRKSGLVPRGSGSHHHHHHGGLNDIF EAQKIEWHE ES4 (1IWLA) Clade B point mutant (SEQ ID NO: 21):  DAASDLKSRLDKVSSFGAGFTQKVTDVQEGQGALAVKRPNLFAWHMTQPD ESILVSDGKTLWFYNPFVEQATATWLKDATGNTPFMLIARNQSSDWQQYN IKQNGDDFVLTPKASNGNLKQFTINVGRDGTIHQFSAVEQDDQRSSYQLK AQ ENLEVDEWAFLF GPPQGVTVDDQRKSGLVPRGSGSHHHHHHGGLNDIF EAQKIEWHE ES4 (1IWLA) Clade C (SEQ ID NO: 22):  DAASDLKSRLDKVSSFGAGFTQKVTDVQEGQGALAVKRPNLFAWHMTQPD ESILVSDGKTLWFYNPFVEQATATWLKDATGNTPFMLIARNQSSDWQQYN IKQNGDDFVLTPKASNGNLKQFTINVGRDGTIHQFSAVEQDDQRSSYQLK AQ ENLAVDSWKNLF GPPQGVTVDDQRKSGLVPRGSGSHHHHHHGGLNDIF EAQKIEWHE ES5 (1D3BB)  ES5 (1D3BB) Clade B (SEQ ID NO: 23):  SKMLQHIDYRMRCIGGAGGIAIGTFKAFGAGMGLILCDCDAFAKIKPKNS KQAEREEKAVG ELLELDKWALL SMTVEGPPPSGLVPRGSGSHHHHHHGGL NDIFEAQKIEWHE  ES5 (1D3BB) Clade B point mutant (SEQ ID NO: 24):  SKMLQHIDYRMRCIGGAGGIAIGTFKAFGAGMGLILCDCDAFAKIKPKNS KQAEREEKAVG ELLELDEWALL SMTVEGPPPSGLVPRGSGSHHHHHHGGL NDIFEAQKIEWHE  ES5 (1D3BB) Clade C (SEQ ID NO: 25):  SKMLQHIDYRMRCIGGAGGIAIGTFKAFGAGMGLILCDCDAFAKIKPKNS KQAEREEKAVG ELLALDSWKNL SMTVEGPPPSGLVPRGSGSHHHHHHGGL NDIFEAQKIEWHE 

Example 7 Identification of VCR1-Like Antibodies

To demonstrate that light heavy chain complementation can be used to identify a VR01, VCR03-like antibody, VRC01/VRC03 chimera were created and expressed (see FIG. 76). The chimeric antibodies were tested for neutralization of HIV constructs (see FIGS. 77-79). The results of the chimeric neutralization studies demonstrated that complementation predicts an antibody as VRC01 and VRC03-like antibodies. Thus complementation is applied to antibody heavy chain sequences generated by 454 sequencing.

454 sequencing was carried out on a sample obtained from subject 45, and 200,000 heavy chain sequences were sorted through these based on threading and retention of specific residues associated with VRC01 and VRC03 to identify VRC01 and VRC03 like antibody sequence. 700 sequences, with a variable sequence identity to VRC01 and VRC03 were obtained. To evaluate whether or not these antibodies can adopt the VRC03 binding mode, their sequences have been “threaded” onto the crystal structure of VRC03/gp120 complex and a so-called threading score was calculated for each of the sequences.

The use of threading technique allow incorporation the structural information into the 454 sequencing analysis and to select the sequences that can potentially adopt the desired binding mode, which has been precisely characterized by the three structures of antibody/gp120 complexes (see Wu et al. Rational Design of Envelope Identifies Broadly Neutralizing Human Monoclonal Antibodies to HIV-1,” Science 329, 856-861 (2010), which is incorporated herein by reference in its entirety and Zhou et al., “Structural Basis for Broad and Potent Neutralization of HIV-1 by Antibody VRC01, Science 329, 811-817 (2010), which is incorporated herein by reference in its entirety). The threading scores range from 0.07 to 0.13, which are in the lower range of the values calculated from the threading of VRC01 and VRC03 and onto each other (The lower the threading score is, the better the sequence matches the structure). This result indicates that these antibodies are be VRC01-like.

A sequence alignment of one of these antibody heavy chains (Antibody Heavy Chain No:57203) is shown in FIG. 80 compared to the amino acid sequences of the heavy chains of VRC01, VRC02, and VRC03 and the germline sequence IGHV1-02*02.IN Antibody Heavy Chain No:57203 was synthesize and a chimera between this heavy chain and the light chain of VRC01 was created. These antibodies were tested for neutralization, when combined with VRC01 light chain (see FIG. 81A-81H). Thus, as disclosed herein, a class of VRC01-like antibodies (heavy chain variable domain only) has been identified.

Below is a list of the heavy chains of VRC01 and VRC03-like antibodies identified. Shown are assigned number of the heavy chain, the deduced germline (germ), the percent identity to VRC01 (seqid1), the percent identity to VRC03 (seqid3), the threading value (thrd1), the divergence from the germline sequence (divg), the nucleic acid sequence identifier and the amino acid sequence identifier.

VRC01 and VRC03-Like Antibodies

The “VRC01 and VRC03-like antibodies” section on pages 91-127 of U.S. patent application Ser. No. 14/864,705, filed Sep. 24, 2015, is incorporated by reference herein in its entirety.

Example 5 Creation of VRC01 and VRC01 Like Multimeric Antibodies

As disclosed herein VRC01, a broadly neutralizing human IgG1 monoclonal antibody against HIV, was cloned from human B cells obtained from an HIV infected donor. VRC01 IgG1 was shown to have very potent neutralization activity against more than 90% of HIV isolates from all clades. This makes it an attractive therapeutic candidate, and a subject for extensive studies aiming to understand the nature of the antigenic stimuli needed to generate VRC01-like antibodies by infection or immunization. This example describes the characterization and development of an IgM antibody carrying the VRC01 V region. We also compare its neutralizing activity against HIV with that of the originally isolated VRC01 IgG1 (see FIG. 92).

The VRC01 V region was cloned into an expression vector containing the constant region from the m chain. The IgM was then produced in 293F cells transiently transfected with this plasmid along with two other plasmids that encoded the VRC01 k light chain and the human J chain, respectively. The IgM was purified by FPLC using a HiTrap IgM column and a Superose-6 size exclusion column.

Secreted pentameric IgM antibodies carrying the VRC01 V region were purified to homogeneity by IgM affinity chromatography followed by size exclusion chromatography. On a molar basis comparison with the VRCO1-IgG, the IgM antibody has increased in vitro neutralizing activity against a panel of VRC01-sensitive and resistant HIV virus strains.

In view of the many possible embodiments to which the principles of our invention may be applied, it should be recognized that illustrated embodiments are only examples of the invention and should not be considered a limitation on the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims. 

We claim:
 1. An isolated nucleic acid molecule, comprising: a nucleotide sequence encoding: an antibody heavy chain variable region comprising a heavy chain complementarity determining region (HCDR) 1, a HCDR2, and a HCDR3, comprising amino acids 26-33, 51-58, and 97-110, of SEQ ID NO: 1, respectively; an antibody light chain variable region comprising a light chain complementarity determining region (LCDR) 1, a LCDR2, and a LCDR3, comprising amino acids 27-30, 48-50, and 87-91, of SEQ ID NO: 2, respectively; or an antibody comprising a heavy chain variable region comprising a HCDR1, a HCDR2, and a HCDR3, comprising amino acids 26-33, 51-58, and 97-110, of SEQ ID NO: 1, respectively, and an antibody light chain variable region comprising a LCDR1, a LCDR2, and a LCDR3, comprising amino acids 27-30, 48-50, and 87-91, of SEQ ID NO: 2, respectively, wherein the antibody specifically binds to gp120.
 2. The isolated nucleic acid molecule of claim 1, wherein the heavy chain variable region comprises the amino acid sequence set forth as SEQ ID NO:
 1. 3. The isolated nucleic acid molecule of claim 1, wherein the light chain variable region comprises the amino acid sequence set forth as SEQ ID NO:
 2. 4. The isolated nucleic acid molecule of claim 1, wherein the heavy chain variable region comprises the amino acid sequence set forth as SEQ ID NO:
 3. 5. The isolated nucleic acid molecule of claim 1, wherein the light chain variable region comprises the amino acid sequence set forth as SEQ ID NO:
 4. 6. The isolated nucleic acid molecule of claim 1, wherein the heavy chain variable region comprises the HCDR1, the HCDR2, and the HCDR3, and an amino acid sequence at least 90% identical to the amino acid sequence set forth as SEQ ID NO:
 1. 7. The isolated nucleic acid molecule of claim 1, wherein the light chain variable region comprises the LCDR1, the LCDR2, and the LCDR3, and an amino acid sequence at least 90% identical to the amino acid sequence set forth as SEQ ID NO:
 2. 8. The isolated nucleic acid molecule of claim 1, comprising: the nucleotide sequence encoding the antibody comprising the heavy chain variable region comprising a HCDR1, a HCDR2, and a HCDR3, comprising amino acids 26-33, 51-58, and 97-110, of SEQ ID NO: 1, respectively, and the antibody light chain variable region comprising a LCDR1, a LCDR2, and a LCDR3, comprising amino acids 27-30, 48-50, and 87-91, of SEQ ID NO: 2, respectively; and wherein the antibody specifically binds to gp120.
 9. The isolated nucleic acid molecule of claim 1, wherein the heavy chain variable region comprises the HCDR1, the HCDR2, and the HCDR3, and an amino acid sequence at least 90% identical to the amino acid sequence set forth as SEQ ID NO: 1; and the light chain variable region comprises the LCDR1, the LCDR2, and the LCDR3, and an amino acid sequence at least 90% identical to the amino acid sequence set forth as SEQ ID NO:
 2. 10. The isolated nucleic acid molecule of claim 1, wherein the heavy chain variable region comprises the amino acid sequence set forth as SEQ ID NO: 1, and the light chain variable region comprises the amino acid sequence set forth as SEQ ID NO:
 2. 11. The isolated nucleic acid molecule of claim 10, wherein the antibody is an IgG, an IgM, or an IgA.
 12. The isolated nucleic acid molecule of claim 11, wherein the antibody is an IgG
 1. 13. An isolated nucleic acid molecule, comprising a nucleotide sequence encoding an antigen binding fragment of the antibody encoded by the nucleic acid molecule of claim
 8. 14. The isolated nucleic acid molecule of claim 13, wherein the antigen binding fragment is a Fab fragment, a Fab′ fragment, a F(ab)′₂ fragment, a single chain Fv protein (scFv), or a disulfide stabilized Fv protein (dsFv).
 15. The isolated nucleic acid molecule of claim 1, wherein the nucleic acid sequence comprises at least one of one of the nucleic acid sequences set forth as SEQ ID NOs: 29-32.
 16. The isolated nucleic acid molecule of claim 1, operably linked to a promoter.
 17. An expression vector comprising the isolated nucleic acid molecule of claim
 1. 18. The expression vector of claim 17, wherein the expression vector is a viral vector.
 19. The expression vector of claim 18, wherein the viral vector is an adeno-associated viral vector.
 20. An isolated host cell transformed with the nucleic acid molecule of claim
 1. 21. A method of making an antibody that specifically binds to gp120, comprising: expressing in a host cell one or more nucleic acid molecules encoding: an antibody heavy chain variable region comprising a heavy chain complementarity determining region (HCDR) 1, a HCDR2, and a HCDR3, comprising amino acids 26-33, 51-58, and 97-110, of SEQ ID NO: 1, respectively; and an antibody light chain variable region comprising a light chain complementarity determining region (LCDR) 1, a LCDR2, and a LCDR3, comprising amino acids 27-30, 48-50, and 87-91, of SEQ ID NO: 2, respectively; and purifying the antibody. 